Romans 12:1-2 teaches us to offer ourselves to God, which pleases Him. Our lives become an act of worship, showing that God is much more valuable than anything on earth. Also, continually renew our mind, though we are new through Christ already (Colossians 3:10, 2 Corinthians 5:17). This is similar to the teaching of getting rid of yeast from the bread without yeast (1 Corinthians 5:7). Then we will know and be satisfied of God’s will.
Note that the will of God has two meanings. One is His sovereign will that’s going to happen no matter what. Such could involve someone sinning. For example, Christ’s crucifixion was God’s plan (Matthew 26:39). For such predestined events to occur, Herod and others had to murder Christ (Acts 4:27-28). Ultimately, it will be for the good. His sovereign plans always happen (Ephesians 1:11, Matthew 10:29, Proverbs 16: 33).
Another meaning of God’s will is what God wants us to do and to be (Matthew 7:21, 1 Thessalonians 4:3). Whoever does the will of God lives forever (1 John 2:17). But many of us don’t, causing lots of pain and suffering. God hates evil behavior, and we need to believe God is sovereign. Ultimately, the evil behaviors are for the good.
In the case of Romans 12:2, to know God’s will is to know what God wants us to be and do, to get our minds renewed so we know what God wants from us; but not to know His sovereign will so we can predict the future.
Renewing our minds requires reading the Bible and learning how to live and do every good work (2 Timothy 3:16).
For things not taught in the Bible, renewing our minds requires praying and asking God to enlighten us so we can infer from the Bible’s teachings on such things.
Renewing our minds also requires us to be transformed because most of our actions are instinctive. So, ask the Holy Spirit to renew and continually transform us (Ephesians 4:23-24, Titus 3:5, Psalm 51:10, 2 Corinthians 3:18). If we ask, God will do it (Matthew 7:9-11). Then we will know God’s will and follow Him spontaneously.
Summary of a sermon by John Piper: