Where must we fix our thoughts

In Philippians 4:8 it says, "And now, dear brothers and sisters, one final thing. Fix your thoughts on what is true, and honorable, and right, and pure, and lovely, and admirable. Think about things that are excellent and worthy of praise."

If we are to do this, mustn't we know where to find such things to think upon?
If God is all of those things, and He reveals Himself to us through His Word and through Jesus, then perhaps those are the places to begin.

Sometimes I wonder if Christians know how serious it is to control what we think, myself included. God doesn't just want purity of body, but of mind and soul. We laugh at dirty jokes, watch movies with too much nudity and violence, and swear without a thought. We must take reign over thoughts. Paul says in 2 Corinthians 10:5 to "take every thought captive so that it is obedient to Christ."

God cares about what we think. He knows how important it is for us to control our thinking. We become what we think about.