“Trust in the Lord with all your heart, and do not rely on your own understanding. Acknowledge him in all your ways, and he will make your paths straight.” (Proverbs 3:5-6)
The key to knowing God’s will is willingness and determination to follow it before knowing it. “If anyone wants to do God’s will, he will know” (John 7:17).
The best indicator as to whether one is really willing to follow God’s will, of course, is whether or not he is now following that part of His will which is already known, as revealed in His Word. This requires first knowing and believing, and then obeying the Word, especially those portions dealing with God’s general will for all Christians. “Your word is a lamp to walk by, and a light to illumine my path.” (Psalm 119:105). Then, if one indeed is following the revealed will of God, he may ask in confidence (1 John 5:14-15) for the Lord to indicate His will in a specific matter on which there is no explicit biblical teaching (see also James 1:5-6).
God will then answer, though it may not be immediately. “they should always pray and not lose heart.” (Luke 18:1). It may not be in accordance with our preferences or personal judgment, but it will always be for the ultimate best. “For we do not know how we should pray, but the Spirit himself…intercedes on behalf of the saints according to God’s will. And we know that all things work together for good for those who love God, who are called according to his purpose” (Romans 8:26-28).
God will lead in two ways in the absence of specific Scripture guidance (which must always take precedence, of course). One is by providential circumstances, the other by inner witness of the Spirit, and these two must agree. Then, if all the terms have been met, one should proceed to follow God’s will as best he can, knowing that God will redirect him if he has made a mistake. God does want us to know His will, and He will “make your paths straight.”