The best way to know God’s will is to be familiar with the Bible. That is because virtually everything you need to know concerning the will of God is in the Bible. If you are totally familiar with the Bible, can interpret it, and understand it clearly, you can know the will of God.
Another way you can know the will of God is through prayer, when you commune with God and learn what pleases Him. The Bible says, “Let the peace of God rule in your hearts” (Colossians 3:15). This means that the peace of God is like a regulator, so that when you violate the will of God, His peace leaves you and you have inner turmoil. You then know immediately that you are going against God’s will. I would say emphatically that the Bible and the peace that comes about through a continuous relationship with God are the best ways of knowing His will.
It is true that God will show us His will through a number of other means. He will show us His will through circumstances. We can also know the will of God through the inner voice of the Spirit as God speaks to us. Sometimes God will send us visions or dreams. He may send us angels or even appear to us Himself. God is infinite, and He can reveal His will to us in many ways.
The key is to be sure that we are submitted to Him and are willing to do whatever He shows us. If we purpose to do His will, we will know His leading.
Finally, for people who seemingly are unable to discern God’s positive directions, I recommend “negative” guidance. Say, “Father, I want Your will above all else. Please do not let me miss Your plan and purpose for my life.” As the writer of Proverbs put it, “Trust in the Lord with all your heart, and lean not on your own understanding; in all your ways acknowledge Him, and He shall direct your paths” (Proverbs 3:5-6).