I like to keep things fairly tidy when I'm working on complex projects and one thing I do 99.99% of the time is set up my Browser a fairly specific way using bins like this:
Sequences - obviously, all of the projects sequences go in here.
Stills - for still images.
Music - for music.
Footage - for your hero footage (usually this has several bins within it).
Backgrounds or Library Footage - In here, if there are animated backgrounds that will be used I dump them into here so I don't have to hunt for them in the Footage bin.
Audio or Sound F/X - In here I put any audio cues or sound effects that the project needs.
Voice Overs - if there are a lot of them or they are really long.
Video F/X - Sometimes, if there are a lot of Motion (.motn) effects files I'll make this folder to keep them all in.
Title Cards - If I'm using LiveType .lpr files for title cards I'll put them in here.
Remember that you can have bins within bins as well to further organize everything. The point is if you start out organized you'll tend to stay organized and that'll save time later on when you need some specific bit of media.