In my walk with the Lord, God has spoken to me through many different vehicles. I feel like I have heard promises or callings from God through; people, the Bible, preachers, and other books. God is omnipresent. He can get a hold of us where ever we are. There is nothing like the feeling when the Holy Spirit speaks a promise directly to your heart.
When I was at church yesterday, I had a moment when God spoke directly to me about an area of my life that I have been neglecting and actually gave me a promise about the future in it.
I don't know how everyone hears from God. He has a different relationship with everyone of His beloved children. Personally, I feel that I tap into God the most when I approach Him with an attitude of praise and worship.
I have found that when God speaks to me regarding a promise for the future, He gives me vision for where He wants to take me. He validates the promise with a feeling of confidence that I am truly hearing from Him and that the thought is not just made up in my head. It is tough to describe the stamp of validation. It is a feeling in the heart that the body cannot naturally generate. It is a resonance with the Holy Spirit inside of my heart.
Proverbs 29:18 (NIV) Where there is no revelation, the people cast off restraint; but blessed is he who keeps the law.
If God did not give us vision or revelation, then we would not have direction at all. Revelation is found in pressing into God. The Holy Spirit is always on time to give us the revelation that we need to carry out God's will for our lives. Our part as believers is to seek God for this revelation and to be obedient to His calling.