Replying to Final Cut Express 4 - Exporting Question

Alright so after playing around in FC4 i've gotten the hang of things but i still do have alot to learn, but my big question here is how do i get a reasonable sized file when i export? so i can put it on like viemo or youtube....i know how to change my settings and all that...i've been trying to do it as a .avi format but its still a huge file...do i have to turn the quality of the video way down low? thanks for the help +karma for helpful replies :)