How do you distinguish between those he sends to you, and those who are trying to trick you?
Great question:
There are a number of ways but first I test them.
1 John 4:1-3 Beloved, do not believe every spirit, but test the spirits to see whether they are from God, because many false prophets have gone out into the world. By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in the flesh is from God; and every spirit that does not confess Jesus is not from God; this is the
spirit of the antichrist, of which you have heard that it is coming, and now it is already in the world.
Now to use this test you must have ears to hear them. So I have them confess the Jesus Christ has come in the flesh. It gets interesting, because sometimes they just flee, but sometimes they will actually say, "I can't tell you that.'' And BTW, make sure they confess Jesus Christ as opposed to just Jesus. I have learned from experience to make sure of that.
Another test I sometimes use, and I know a number of Christians who do use this first, is from 1 Cor 12:3 Therefore, I make known to you that no one speaking by the Spirit of God says, “Jesus is accursed”; and no one can say, “Jesus is Lord,” except by the Holy Spirit. Again, it is not quite so obvious and seems to be assumed, but I use Jesus Christ is Lord as opposed to just Jesus. Of course demons are not actually serving any Jesus but Satan, so perhaps it is more than needed, but when I use that test I use "Jesus Christ"
Now there also comes the experience factor as to when to use those tests.
Heb 5:14 But solid food is for the mature, who because of practice have their senses trained to discern good and evil.
The more you use your spiritual senses, which includes hearing with your spiritual ears, the better you are at discerning between good and evil. Still, don't let that completely stop you from testing the spirits!!
Another thing is that the Lord usually tells you when He is sending an angel of angels to you.
Now you might also be asking Him for the Kingdom come, and if you ask you are going to receive if you abide in His word (the Lord Jesus Christ is the Word of God), so I often get angels right after I ask for them - or pray Thy Kingdom Come. We often don't think about this much, but we have access to God's Kingdom, so praying "Thy Kingdom Come" is available for us to pray at any time. In fact if we become more familiar with His Kingdom we can ask for certain help - eg certain angels.
It is written that what is loose in heaven is loosed on earth, so we can ask for angels to be loosed on earth and get our request answered. So let's say you know someone that just seems to need to joy in their life - you can ask the King of kings, Jesus Christ, to send Joy (angels of Joy) to that someone. Now again, some experience is valuable. Doesn't Jesus Christ know better than you what is needed? So, I have found it better, after some experience, to ask the Lord to do what He thinks is best in most situations.
There is much more that can be said about this, but first let us start seeking the Kingdom of God ourselves and won't the King show you all the above and more? He did me.