Revelation by the Holy Spirit
"Now when they had gone through Phrygia and the region of Galatia, they were forbidden by the Holy Spirit to preach the word in Asia. After they had come to Mysia, they tried to go into Bithynia, but the Spirit did not permit them. So passing by Mysia, they came down to Troas. And a vision appeared to Paul in the night. A man of Macedonia stood and pleaded with him, saying, "Come over to Macedonia and help us." Now after he had seen the vision, immediately we sought to go to Macedonia, concluding that the Lord had called us to preach the gospel to them." (Acts 16:6-10)
As mentioned earlier, God will always find a way to disclose His own will to a God-fearing person. In the Old Testament times, the infinite God often disclosed His will to His servants through prophets, or priests by way of Urim, visions, or dreams. Especially in Genesis, we note the appearances of angels as well as God personally speaking to His servants. In the New Testament times before the descent of the Holy Spirit, dreams were rather common - for instance, Joseph had several dreams (Matt. 1:20-23; 2:13, 19, 22). After the descent of the Holy Spirit, there were occasions when angels delivered God's messages regarding exceptionally important matters or when even the Lord Himself personally appeared (as recorded in Acts 9:4-5, 23:11, 27:23 and in II Tim. 4:17 when the Lord spoke directly to Paul). There were also times when God used visions - such as Paul's Macedonia vision (Acts 16:9) and Peter's vision in Acts Chapter 10.
Since the descent of the Holy Spirit, God's will is usually revealed in our inner depth (the spirit) through the generating of urging sensations, inspirations or restraints by the Holy Spirit. At times, the Holy Spirit urges us: for instance, Jesus was "driven" to the wilderness to be tempted by Satan (Mark 1:12). At times, the Holy Spirit forbids us - for instance, Acts chapter 16 tells us that the Holy Spirit did not permit Paul and Timothy to preach in Asia or to go to Bithynia. By urging or restraining, the Holy Spirit generates a spiritual (inner) inclination.
Should one be uncertain, unclear, or skeptical if such inner sensations are really from the Holy Spirit, he could ask of the Lord. After fervent prayers, they will vanish if they originated from Satan or oneself. If, however, they were from God, they will grow stronger and clearer.
Let me add that as long as your heart is perfect and totally focused on God's will, there is no need to fret. Moreover, even if you did indeed misinterpret, you will develop a sense of disgust - you should then stop what you were doing. You need not fear because God will be responsible for steering you to the right track. Take the case of Jonah, for example: though Jonah knew that God sent him to deliver His message to Nineveh, he tried to escape to Tarshish because he had not yet fully comprehended God's compassion and righteousness (Jonah 4:2.). Even so, God's loving hand had arranged circumstances to bring him back on the right track.
A person who is living a godly life may sometimes act according to his heart's desire. If his desire is not in God's will, God will let him know. A good example is King David's desire to build the temple for God. Even though God did not permit him to do so, David was greatly blessed for his loving heart (ref. I Chr. 17:2-27).
The Lord's servant John Song (1901-1944) was once asked, "How do you know God's will?" He replied, "When I studied God's words, prayed and had communion with the Lord, I got a sudden sensation or inner feeling that later proved to be the will of God." (The "sudden sensation" is another way of saying "God revealed His will in my spirit." The sensation was later proven to be God's will through God's control of circumstances and His anointed presence.)
It is usually when we draw near to God, study God's words, pray, gather in fellowship, or worship (especially during early morning devotion) that God inspires us. There are a few exceptions; such as at times of danger (Acts 23:11; II Tim. 4:17; Acts 27:23), special callings (Acts 8:26; Acts 11:5; Acts 13:2), or interventions by God. They are always consistent with biblical principles and accompanied with a deep sensation of peace.