Knowing God's will is primarily a matter of conforming your heart and life to His revealed will in Scripture, rather than searching for secret, hidden decrees. While Reformed traditions emphasize the sufficiency of the Word, all agree that we must prayerfully seek the Holy Spirit's guidance to submit our desires to His sovereign and revealed commands.
The primary way we know God's will is through the revelation He has already given us in Holy Scripture. As the Westminster Shorter Catechism — Question 39 states, the duty required of man is obedience to His revealed will. We do not need to look for signs or hidden messages, for God has graciously provided everything we need for life and godliness within the pages of the Bible. The gospel reminds us that because we are accepted in Christ, our pursuit of obedience is not a way to earn God's favor, but a joyful response to the grace we have already received.
Because our own wills are often clouded by sin and self-interest, we must rely on the Holy Spirit to align our hearts with God's. We pray for this in the third petition of the Lord's Prayer, as reflected in the Westminster Shorter Catechism — Question 103, asking that God would make us both able and willing to submit to His will. This prayer is an acknowledgment of our own inability and a radical trust in Christ, who perfectly did the Father's will on our behalf. When we feel uncertain about a direction in life, we are invited to bring that burden to Him in prayer, trusting that He is working in us both to will and to work for His good pleasure, as noted in the Second Helvetic Confession — CHAPTER IX.