Discerning spirits and false prophets?

How can we tell if a spirit is from God, how can we discern false prophets? It's not always easy, as indicated by Jeremiah thinking some false prophets were real ones!
 
Jer. 14:13-14  But I said, "Ah, Sovereign Lord, the prophets keep telling them, 'You will not see the sword or suffer famine. Indeed, I will give you lasting peace in this place.'"  Then the Lord said to me, "The prophets are prophesying lies in my name. I have not sent them or appointed them or spoken to them."
 
We do have instructions on this, though:
 
MT 7:16 By their fruit you will recognize them.
 
Do they bring the fruit of the Spirit, love, joy, peace, and so on (Gal. 5)?
 
Also, true believers are promised protection in not being deceived, so that is reassuring!
 
MT 24:24 For false Christs and false prophets will appear and perform great signs and miracles to deceive even the elect--if that were possible.
 
Some believers also have a special gift for discerning spirits (1 Cor. 12:9), and we can check with them. And the taste, or the quality of God's word is distinct (cf. Heb. 5:14):
 
Jeremiah 23:28-29  Let the prophet who has a dream tell his dream, but let the one who has my word speak it faithfully. For what has straw to do with grain?" declares the Lord.  "Is not my word like fire," declares the Lord, "and like a hammer that breaks a rock in pieces?
 
So the effect and the resemblance of and given message to fire, to a hammer, will be evident. For example, as C.S. Lewis said of various sayings attributed to Jesus, "It's a good saying, but not his," that aspect must line up.
 
1 John is a good resource as well, here is a rather extended passage:
 
1 John 4:1-6  Dear friends, 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.  This is how you can recognize the Spirit of God: Every spirit that acknowledges that Jesus Christ has come in the flesh is from God,  but every spirit that does not acknowledge Jesus is not from God. This is the spirit of the antichrist, which you have heard is coming and even now is already in the world.  You, dear children, are from God and have overcome them, because the one who is in you is greater than the one who is in the world.  They are from the world and therefore speak from the viewpoint of the world, and the world listens to them.  We are from God, and whoever knows God listens to us; but whoever is not from God does not listen to us. This is how we recognize the Spirit of truth and the spirit of falsehood.
 
We may pick out the parts to apply here! And one more:
 
Matthew 7:15-20  Watch out for false prophets. They come to you in sheep's clothing, but inwardly they are ferocious wolves.  By their fruit you will recognize them. Do people pick grapes from thornbushes, or figs from thistles?  Likewise every good tree bears good fruit, but a bad tree bears bad fruit.  A good tree cannot bear bad fruit, and a bad tree cannot bear good fruit.  Every tree that does not bear good fruit is cut down and thrown into the fire.  Thus, by their fruit you will recognize them.
 
And this can be applied to prophets, and to voices people hear, too, what deeds tend to be associated with them, do these beings, or prophets, show good fruit?
 
And finally, people are encouraged to ask for confirmation, in various instances, supernatural confirmation, if need be:
 
Exodus 4:1-5  Moses answered, "What if they do not believe me or listen to me and say, 'The Lord did not appear to you'?"  Then the Lord said to him, "What is that in your hand?" "A staff," he replied.  The Lord said, "Throw it on the ground." Moses threw it on the ground and it became a snake, and he ran from it.  Then the Lord said to him, "Reach out your hand and take it by the tail." So Moses reached out and took hold of the snake and it turned back into a staff in his hand.  "This," said the Lord, "is so that they may believe that the Lord, the God of their fathers-- the God of Abraham, the God of Isaac and the God of Jacob-- has appeared to you."
 
Here is another way to tell, false prophets are generally popular:
 
LK 6:26 Woe to you when all men speak well of you, for that is how their fathers treated the false prophets.
 
And here is a critical test:
 
1JN 4:2 This is how you can recognize the Spirit of God: Every spirit that acknowledges that Jesus Christ has come in the flesh is from God.
Do they accept the historical presence of Jesus, and his coming into the world?
 
A missionary in Ethiopia tells of applying this test when people would speak somehow supernaturally, and demonic spirits simply couldn't do this.
And even more, do they make us think not so much of them, but more of Jesus, is he more real to us as a result of what they say and do, do we know Christ and love him more? That is the best fruit:
 
REV 19:10 "Worship God! For the testimony of Jesus is the spirit of prophecy."