I highly recommend that any aspiring film composer (and filmaker as well) watch this great interview with John Williams at USC's Thornton School of Music. There's 6 parts and an Introduction. It really gives alot of insight into the process of film music, as well as John Williams' own approaches.
If you don't know who John Williams is, leave now. You're not cool.
Here's the link:
http://homepage.mac.com/smptv/J.Williams_career.html