So this is going to sound funny (no pun intended). You've probably never been advised to dress like a cartoon...but watching your favorite animated program can be a lesson in proper-fitting clothing! Don't ask me where I get this stuff...but most cartoon characters have perfectly fitting clothing (I know, because they don't have bodies).
The lesson here is that your clothing should follow the natural lines of your body. Your shoulder seams should hit at your shoulder (not hang off), your inseam should cover your leg (not too short showing your socks, and not too long bunching up at your shoes), your sleeves should hit straight down at your wrist (not bunch-up or hang into your hands), your collar should fit your neck (not hang off), etc.
Even Homer has a great tailor.
Yours in style,