Here's some advice for beginning guitar players, even if you've already been playing for a couple of years or so.
1. Get the best quality guitar you can afford when starting to learn. It's easier to sell a good guitar if you decide you don't want to continue later on. Some of the high price acoustic manufacturers now make an entry level version, like Martin, Taylor, Washburn, with a lifetime warranty.
1a. Holding the guitar. Your fretboard hand knuckles should be parallel to the length of the fretboard (as much as possible). Your 4th pinky finger is an important playing tool, not just bent backwards out of play. Thumb goes centered under the neck; that's how you'll find the strenght to push down on the strings with your other fingers. Prop your leg (fret side) up if you have to, with the neck higher in the air. In Spain (where the guitar originated), a small foot stool is used to prop the fret side leg up. Train don't strain. Hand muscles need time for stretching and developing strength, just like any other physical workout. You can injure your hands if you try too hard. Get a hand cramp, rest it fully before starting again. Use Lemon Pledge or equivalent to clean your guitar AND strings after playing (finger sweat and dirt does get on the strings to make them tarnish faster).
2. If you get an electric guitar to learn, don't turn the distortion up. I hear beginners doing this all the time in music shops. Why not do it? It destroys your beginning ear training. Need to hear the notes clearly when learning; reveals pick and fret hand mistakes, makes you play clean without mistakes. Then when you get better, you'll find you don't need near as much distortion to try and mimic your favorite rock icons. Won't miss as many notes either.
3. Get a tuning fork and learn to use it, not an electric tuner. Why? Using a tuning fork = ear training. After a while, you'll get to where you can tune your guitar to that same tuning fork note, without a tuning fork. THEN... you've got a solid note reference in your head to use for further ear training. It's all about sound afterall. Never play your guitar out-of-tune when learning; kiss your ear training goodbye if you do (this further cements need for a quality guitar that can be in good tune).
4. Before you get disgusted with learning to play guitar, give it a chance by doing a warmup finger exercise for a few weeks, every time when you first pick it up to play. Here's an easy one:
5th Fret - 6th Fret - 7th Fret - 8th Fret
1st finger-2nd finger-3rd finger-4th finger (pinky)
Wherever your 1st finger is planted on the fretboard, that's what guitar positon it is. So that's the 5th position (5th fret).
The idea is to pick each note clean (no mistakes), slowly, and leave fret finger down as long as possible to sound the note legato (long) while you get ready to plant the next finger. Play the notes across the fretboard in the position, one finger per fret across the fretboard. Fret finger should be placed just behind the fret to assure a clean note; not on or touching the fret, but just behind it. Then reverse the pattern playing single notes across the fretboard, low bass string through little E string then back up. Picking hand should be alternate picking only. No picking only downward or upward. Doing this slow means speed and ease later.
That warmup loosens the fingers up more so it makes forming chords much, much easier. It'll also help to learn scales later if you decide to stay with the guitar.
5. Get a songbook with songs you LIKE, that you KNOW, and that you can SING. I don't mean songs like Ol' McDonald or Mary Had A Little Lamb either. I learned using songbooks of Bob Dylan and Crosby, Stills, Nash, and Young. Had the records for those songbooks too. Those songbooks have the chord graphs above the lyrics and music, and most often, the time with the lyrics are accurate. Match those chord changes of the chord graphs with the lyric timing, and learn to sing and play rhythm at the same time. That's the fastest way to advance. Ideally, you wanted to learn guitar so you could play songs you like, right?
6. Rhythm secrets - another thing the alternate picking exercise does is to help you learn timing. It also translates later to strumming chords. Fast chord rhythm is done with the pick hand alternating across the strings, not the hand chopping the strings only up or only downward (though that is done on some songs as an effect, but not the majority of song rhythms). When you can get rhythms like Doobie Brother's Listen to The Music, or Long Train Running correct, then you'll know what I mean.
7. OK, you've got a computer (most likely if your reading this). Lot of simple 'free' music programs out there that you can type chords into, pick a music style, and play drums and bass, et al for you. Those are good 'timing' practice tools. Not essential, but just another way to learn timing. Otherwise, you'll need a metranome. Can buy one the size of a credit card that puts out a click tone, and change bpm (beat per minute). It's important that you do one or the other when learning. Here's a story why...
A mix/mastering engineer friend of mine for an Indie label in Nashville handed me some tracks of a solo guitarist/singer who they put a band behind and recorded some of his songs. The guy flat refused to play to a 'click' in the studio. That click is just a low-level metronome tone played in everyone's headset during recording; helps everyone stay in time. The guy's songs were great, but the band behind him sounded like they were playing musical chairs, simply because his timing was terrible. It was impossible for the band to follow his time, even though they tried. And it's mainly because the guy had played and sang so long by himself, and without anything to keep time, that he no longer noticed it. Lot of professionals that don't need a 'click' in the studio is because they had... learned good timing by years of playing with a steady metronome, etc.
Your in luck today, I feel like teaching.
8. Basic Music Theory:
A. Western music is based on the ancient Greek modes, and we call it Western Diatonic Harmony. Why's knowing this important? Because each one of those 7 Modes of the Major Scale has a different tonal sound, even though they're within the same Major Scale.
B. The Major Scale is based on the first Greek Mode, called Ionian. The key of C Major is: C-D-E--F-G-A-B--C. No sharps or flat notes in C Major. If you play on one of your E-strings open, that open note is E. Then the 1st fret if the note F, then on the 3rd fret it's G, etc. Space from one fret to the next is called a 'half-step'. Space between two frets (like 1st fret to 3rd fret) is called a 'whole-step'. If you'll notice, everywhere on the fretboard where the interval from E to F or B to C occurs, it's always a half-step, or one fret. That's a musical constant for all... instruments. It never changes. (Don't worry about the # or b notes in between on the fretboard just yet, called Accidentals).
C. Scale notes have Degree numbers assigned to them - the 8th (Octave) is a repeat note of the 1st note, but higher in pitch:
1 - 2 - 3 - 4 - 5 - 6 - 7 - 8
C - D - E- F -G - A- B - C
The reason why we have sharp (#) and flat (B) keys, is because of how the note intervals fall between those notes of the Major Scale. What makes the Major Scale from the Ionian Mode sound is where... those E-F and B-C half-steps fall. So to spell the other keys, you've got to maintain that same Major Ionian interval relationship, with the half-steps between the E-F and B-C notes. With the Major Scale, that's always between the 3rd and 4th, and 7th and 8th degrees (like above).
Look at the key of G Major:
1 - 2 - 3 - 4 - 5 - 6 - 7 - 8
G -A - B - C- D -E -F# - G
You want the half-steps only between the 3rd-4th and 7th-8th degrees of the scale (for Major Scale). But the E-F falls between 6-7th degrees in the key of G, so the F had to become an F# to keep that Major Diatonic relationship. And thusly, the key of G Major has one sharp, an F#. All the other keys also require flatting or sharping to keep that half-step relationship between the 3-4 and 7-8 degrees for Major harmony. This is for all musical instruments, not just guitar. That's usually where I start out students with Music Theory. Spell the 12 Major keys, putting the sharps and flats in where they're required. Doing that is what cements understanding of what's to follow, because all... music, even chords and arpeggios have their basis from the musical Scale.
D. Chords - Arpeggios:
There's only 3 main musical tools that make up the whole basis playing music, the Scale, Chords, and Arpeggios. Chords mean stacked notes, notes played at the same time. An Arpeggio is simply a chord where you pick single notes out of it, playing it like a scale one note after the other. So Chords are vertical harmony, whereas the Scale is horizontal harmony.
A Chord has a minimum of 3 notes, called a Triad, and they're stacked on top of each other played at the same time. Only 2 notes is an Interval, and it is not... a Chord. A Chord is spelled from the Scale by skipping every other note (for Major Harmony). The reason the Triad is the basis for all Chords is because there's only 4 different Triads in music: Major, Minor, Diminished, and Augmented:
Major Triad - C-E-G = C Major Chord
Minor Triad C-Eb-G = C Minor Chord
Diminished Triad C-Eb-Gb = G Dim Chord
Augmented Triad C-E-G# = G Aug
Notice how those Chord notes come from the Scale to spell them, starting with the 1 and then skipping every other note...
1 - 2 - 3 - 4 - 5 - 6 - 7 - 8
C - D- E- F - G - A- B - C
C Major Chord = the 1 - 3 - 5 notes of the C Major Scale.
C Minor Chord = the 1 - b3rd - 5 notes of that same Scale.
C Dim Chord = the 1 - b3rd - b5th of that same Scale.
C Aug Chord = the 1 - 3 - #5 of that scale.
By understanding the Degree numbers for the notes in the Scale, you can easily learn how to spell ALL... chords. Learn what sharps or flats are in the other Major Scales, and the same degree formula for Chord spelling applies. A Major Chord, regardless of what Key, is always... the 1-3-5 notes of that Key's Scale. So in G Major its first Chord would be 1-G, 3-B, 5-D. The degrees 1-3-5, easy. The Minor chord difference is the 3rd is flatted (B), so its formula is a 1-b3rd-5 of the Key's Scale, always. Same applies for the Diminished and Augmented Chord Triads.
E. Chord Embellishment:
So how do you get bigger chords like C Major 7th, or C Dominant 7th (C7), or Cmin9, or C13, etc.? Simple, you keep adding more notes from the same Scale they come from, using the every-other-note principle. Embellishment also means extending the Scale into the next Octave higher in pitch (same note names, just at a higher pitch range). So all you're doing is taking one of the FOUR basic Triads, and stacking more notes on it:
1 - 3 - 5 - 7
C - E - G - B = CMaj7 or C Major 7th Chord
That's called 7th Harmony, because you've added the 7th note of the Scale.
1 - 3 - 5 - 7 - 9
C - E- G - B - D = CMaj9 or C Major 9th Chord
That's embellished, because now you're into the next Octave with that 9th note, which is D, also the same note as the 2. The only difference is, that 9th pitch is higher than the 2nd that's next to the 1.
F. Harmonized Major Scale:
All that means is spelling all the chords on the separate Degrees of the Scale, like this:
1st Degree C (add every other note up to the 7th) = C-E-G-B = a CMaj7th Chord
2nd Degree D = D-F-A-C = Dminor7th Chord
Wait! Why's that D chord different? Got to use ONLY the Scale notes you're spelling from, in this case C Major Scale. How many sharps or flats does C Major have in it? NONE. But when you spell the C Major Harmonized Chords, the first note STILL ... is coming from its OWN Scale. In this case the 2nd degree with the D note (in C Major) has to use only the C Major Scale notes. But... the intervals of the D Chord are named... from the D Major Scale. May have to read that a few times and look at the example to get it. If you spelled the Major keys already, should be easy to understand.
next...
3rd Degree E note = E-G-B-D = Eminor7th Chord (same situation, this chord spelled from using key of E Major)
4th Degree F note = F-A-C-E = FMajor7th
5th Degree G note = G-B-D-F = G Dominant 7 or G7
6th Degree A note = A-C-E-G = Amin7 or A Minor 7th
7th Degree B note = B-D-F-A = Bmin-5 or B Minor b5 or Half-Diminished chord
We see with adding the 7th note of the Scale onto the Triad, lot of variations start appearing. Things get interesting.
The G7 or G Dominant 7th Chord, has a flatted F. Remember in the Key of G Major, the F# note is natural to its Key? Yet here in C Major Harmony, got to use a natural F, not an F#. Thus, the F is not sharped on the 5th Degree Chord of C Major. And between the G7 chord's 3rd (B) and that flatted F, it produces a Tritone interval. Play a B note and a F# note together, and you'll quickly hear what I mean. The two notes rub against each other when sounding, and that's where the Dominant sound in the chord comes from. It's sound is like the chord needs to resolve somewhere else, to another type chord (most often the 1 chord).
With adding a b7th onto the Minor Triad, like C-Eb-G-Bb, it smooths out the Minor Triad sound quite a bit. It's still a Minor Chord though.
G. Common Note Chords
If you look closely at the 1 Degree chord notes, and the 3rd Degree, and 6th Degree chords, you'll notice they all have at least... two notes common with each other. Same goes for the 2 Degree chord and the 4 Degree chord. The for the Dominant sound, the 5 Degree chord and the 7th Degree chord have common tones in them.
This means there are ONLY 3 FAMILIES of Chords. By Family means they can be exchanged for each other, because each group has common tones in it giving a very near close to each sound. These are the 3 Family chord groups in the key of C Major:
The Major Chord Family = CMaj7, Emin7, Amin7
The Minor Chord Family = Dmin7, FMaj7
The Dominant Chord Family = G7, Bmin7b5
How's that useful?
Ex.: You're trying to learn a song off the radio, and hear the bass tone of what Chord is being played, but you can't quite get what kind of chord you're hearing. Well, there's only 3 Chord Families to try, either the Major, Minor, or Dominant groups of chords. So just pick one, and your ear ought to immediately hear the difference. For example, a Major chord sound happy, lively, but a Minor chord sounds sad, dark. And a Dominant chord sounds leading, like it wants to go somewhere, anywhere but staying on that Dominant sound.
You find what Family the chord is in first. Most often the bass is playing the root note of the chord in most modern music. Then you try the 7th version of the chord, like min7th or major7th, or dominant 7th. Then maybe an embellishment of the chord type, like min9th, dom13, maj11th, etc. Even with those embellished versions, you're still staying in the basic Chord Family. After a while, depending on what style(s) of music you listen to, you may start hearing altered notes in the chord too, like G7b5#9 or C11#9, etc.
Joe Walsh used a Dom7#5 chord in the song Funk 49 when he played with the James Gang. Jimi Hendrix used a lot of Dom9th and altered dominant chords as he originally wanted to play Jazz-Fusion. Those altered chords are Real Harmony per music theory. It's just that they originate from different Harmonized Scales, like the Harmonic Minor Scale and Melodic Minor Scales.