In the book of Acts, God gave direction to His disciples, and not just through Scripture. He also spoke directly into their hearts. For example, Ananias was told to go to the street called Straight and pray for Saul, Acts 9:11. Paul was told to go to Macedonia, Acts 16:9. I believe that God can speak to us today also, and direct our hearts.
But how do you discern whether something is from God, or from you, or from Satan?
There are several ways something from Satan can be discerned. First, judge it by its character. Satan is a liar and the author of lies, John 8:44. He causes confusion, James 3:15-16. He comes to kill, steal and destroy, John 10:10. Satan is pushy, always seeking a way to attack, 1 Peter 5:8-9. Be warned, Satan can quote Scripture, Matthew 4:1-19 and do miracles, Exodus 7:11. He cannot, however, imitate God's peace, James 3:17-18. If there is no peace, that is not God.
Also, Jesus said we could judge something by its fruit, Matt. 7:16. Always ask, "What is the fruit in me?" If something causes you to despair, or feel confused or cut off from God, then that is not a word from God.
Contrast this to God's character. God is love, 1 John 4:8. God's purpose, even in correction is always to restore, Gal. 6:1. The Lord NEVER condemns His children, Romans 8:1. Anyone who cries out to Jesus Christ is saved, Romans 10:13, and God promises that He will never leave them or forsake them, Hebrews 13:5.
Jesus Christ came so that we could have life and that abundantly, John 10:10. God is never pushy, He never violates our free will, Rev. 3:20. Moreover, any direction or counsel which is from God will ALWAYS line up with the Word of God, and will ALWAYS--no exceptions--come with peace, James 3:17-18.
If something is from the Lord, there will be a witness in your spirit, for the Holy Spirit is within you if you belong to Christ, Romans 8:9, and He affirms His counsel. On the other hand, if something is from Satan, there will be a disquiet, an edginess--again the Holy Spirit within you discerning something is wrong. Also, no demon can ever say that Jesus Christ is Lord, or that He has come in the flesh, 1 John 4:1-3; 1 Cor. 12:3. If (out loud) you command that spirit to tell you whether or not Jesus Christ is Lord and if He has come in the flesh, if that spirit is demonic, it will either leave immediately or deny the Lordship of Jesus Christ. On the other hand, if that spirit is the Holy Spirit, then He will affirm those two truths, and let you know also that He is pleased with you for testing the spirits, as He directs, 1 John 4:1.
What to do if something is demonic? Resist it. First make sure you are clean--confess all sin, 1 John 1:9. I also recommend asking God to cover you with the blood of Jesus and put a hedge of protection around you (Job 1:5,10 is an example of a hedge of protection because of sacrifice). Then use James 4:7-8 and tell that demon spirit to leave, in Jesus Christ's name. Do this out loud, because although demons can interject thoughts into your mind, I don't believe they can hear you think. Even quote this Scripture to it, something like, "You demon spirit that just said such-and-such, I resist you now in Jesus Christ's name, and I command you to leave. Scripture says, "resist the devil and he will flee from you." I am resisting you now, and in Jesus Christ's name I command you to GO!"
Then obey the last part of James 4:7-8--draw near to God. The quickest way to draw near to God I've found is to praise Him, Ps. 22:3, KJV, but reading or reciting Scripture is also effective.
When commanded to go in Jesus' name, demons have to flee. A born-again child of God has incredible authority in the Spirit. But we must use it. We are told to put on the armor of God, we are told to take up the sword of the Spirit which is the Word of God, Eph. 6:10-18, and we are told to resist the devil and he will flee from us, James 4:7-8. This authority is ours, in Jesus Christ's name, but we must use it.
Recall that 1 Thessalonians 5:23 indicates that we are spirits, we have souls and we live in a body. If your spirit belongs to Christ, then God will speak into your spirit, and give you His deep counsel, Prov. 20:27. Most often this guidance will be a witness in your spirit, or a quickening of Scripture to you. It can be that "still small voice" Elijah heard in his heart, 1 Kings 19:12. It can also be a dream, a vison or even an audible voice.
There is a third source of guidance--our own soul. The soul is the mind, the will, and the emotions--any of these can be full of the "old man" Eph. 4 and Col. 3 talk about. How to discern what is from us and what is from the Lord? I think with time and experience this becomes much easier--look at Hebrews 5:14, where it talks about "those who by reason of use have their senses exercised to discern both good and evil." These are also those who are in the "meat" of God's Word.
Also, something I do when I need to hear from God and I do NOT want my soul to get in the way: I tell God about all my own thoughts or good ideas--and then I put all of that on the altar. I tell the Lord that I will do NONE of them, unless He directs me. Then I pray and wait. Sometimes He speaks to me immediately, other times I may hear Him through Scripture, my husband or another Christian, confirming something He wants me to do. Other times I just need to be patient and wait. He is so good. I have never known Him to not answer when I have cried out to Him and asked Him for direction.
Our God promises, "I will instruct you and teach you in the way you should go, I will counsel you and guide you with My eye," Psalm 32:8. Jesus said, "My sheep hear My voice," John 10:3, 16, 27. There is a condition, however--we must listen. Also, we must be willing to do as Scripture directs--to test the spirits, 1 John 4:1, and to resist anything that comes from our enemy, James 4:7-8.
One last thought. I was having trouble hearing God's voice, and I asked Him why. His answer changed me. He said that I was in the world a lot, listening to the world--television, newspapers, etc., and almost never in the Word, listening to Him. The Bible is God's Word to us. I felt that God instructed me to "fast" newspapers and TV for a while, and just read my Bible. Sure enough, reading the Word of God cleaned out my spiritual ears. When you listen to God's voice in the Word, you are hearing the voice of the Lord. It is so easy then to hear His voice in your heart as well--to bring Scripture to remembrance, to counsel you, to give you direction.
Our God is so good. Jesus said He would not leave us as orphans, but He would send the Holy Spirit to lead us and guide us into all truth, John 14:18; 16:13. He still speaks to us today, but we must listen.