Romans 12:2 (new century version)

Do not be shaped by this world; instead be changed within by a new way of thinking...

whin i hear this i think it means something like, Be numb to the temptations the world throws at you by changing the way you think in with your brain and in your heart. The verse ten continues on, saying:

...Then you will be able to decide what God wants for you; you will know what is good and pleasing to him and what is perfect.

So, to me, changing the way you think so that you know what pleases God means to study the bible and change your heart according to the bible. You need to truely be in love with God and truely seek him by reading his word and putting it in your heart, not just your brain. And something to add to this note, just because you look like a christian and put scriptures in your memory doesnt mean you are a TRUE christian. To be a true christian you cant just place scriptures in your mind, you need to lock them in your heart.
*Psalms 119:11- I have taken your words to heart so i would not sin against you
If God's word is only in your mind its just sitting ther, useless. Its like knowing what pleases God, but not really caring if you do. Putting it in your heart is changing the way you think in your mind and changing the way you take on life. It means your really trying not to sin agains God

Dont try to pretend you changed the way you think if you put on a good show when people are watching, but change as soon as you are in the comfort of your own home. Again you memorized the scriptures in your mind but havent put them to use...which is no good.
*James 1:22-Do what God says; when you only listen and do nothing you are fooling yourself
so if you know Gods word and dont do what it says, you are fooling you, not God
*James 2:14-My brothers and sisters, if people say they have faith, but do nothing, their faith is worth nothing
So if you claim to be a christian, but its not in your heart, it means nothing
Again dont pretend because God knows the truth and thats all that matters, he knows what your heart holds
*1 Samuel 16:7-...for a man looks at the outward apperence, but the lord at the heart.