ok..quick rundown..if you need help, hit me up on AIM.
a. sig is too big...generally, large sigs = beginner
b. because sig is too big, you think you have all this room to play with and HAVE to fill up, so you put random shit in there
c. it is usually, almost always, a bad idea to:
1. bold/emboss your render
2. brush or filter over your render
d. less is more. you'll see the more "professional" sigs dont really have alot going on, other than background and blending techniques
c. pick renders that you feel you can create motion with, and have a good focal point