My friend and I had a long conversation a few days ago about this stuff...
We finally decided that part of our problem, as teenagers fighting some hard battles between those ever-warring flesh and spirit, is this: If we want to live in the Spirit, then why do we feed the flesh??
The more new clothes I buy, the more I want. The more time I spend hanging out with people who breathe sinful things (swearing, dirty jokes, etc...) WITHOUT the purpose of being a light for them (as opposed to just ..well, hanging out), the more I find myself doing the very same things in my mind - I swore out loud in one of my dreams a night or two ago. Was a wake up call, pardon the pun

The more I watch questionable movies, the more I desensitize myself to the fallicy of worldly things.
I don't know how to fix myself, but I'm glad that as long as I spend all my energies on God, more and more, He will fix me Himself! My advice? Since our attractions are determined by our values, and our values come from whatever we spend the most time doing and thinking about...then think about Him! It's a small step

And the only advice I know how to give...