Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect. – Romans 12.2

Not conformed . . . but transformed
This is the difference between an outward conformity or disguise and a thorough inward assimilation. As Christians we’re not to copy the fleeting fashions of the present time, but be completely changed in view of that higher mode of existence, in strict accordance with God’s will, that He has chosen. “To be conformed to this world” is to act as other people do, in opposition to this Paul exhorts us to undergo a complete and total change which will align us more into accordance with the will of God.

The “world”
World refers to the popular worldview that rejects God and His revelation. When we’re unbelievers, we’re naturally conformed to the world (Ephesians 2:1–3). As believers, we are no longer conformed to this world because we no longer belong to the spirit of this age. We have been translated from the kingdom of darkness into the kingdom of God’s beloved Son (Colossians 1:13). Therefore, rather than continuing to conform to this world, we are to be transformed by having our minds renewed.

Renewing of your mind
The mind is the key to the Christian life. The reason why non-Christians do not respond to Christian truth is that they cannot discern spiritual truth (1 Corinthians 2:14). The gospel is a call for the unbeliever to repent of his sin and embrace Christ by faith. As I’ve mentioned before “repentance” means we have a changing of mind. So our thinking must be changed (transformed) from old, ungodly ways of thinking into new, godly ways of thinking. What we know in our minds to be true forms a conviction in our hearts of that truth, and that conviction in our hearts translates into action. Remember that it’s the “helmet” of salvation, therefore, we must first renew our minds.

Conclusion
The only way to replace the world’s way of thinking is to replace it with God’s truth, and the only infallible source of God’s truth is His revealed Word. Transformation through a renewed mind comes as we, as believers, expose ourselves to God’s Word through the faithful teaching of it each week in church, personal Bible study, and group Bible study. A solid church that believes in preaching the Word, reading the Word, and singing the Word is invaluable in helping us to renew our minds.
There is no magical formula for renewing our minds, no 12 steps. We have to fill our minds with God’s Word. As Jesus prayed to the Father, “Sanctify them in the truth; your word is truth” (John 17:17).