Here are some very detailed walkthroughs that will tell you all you need to know about each topic. I've used them myself and they told me exactly what I wanted to know. Also these were written by a kid whos played the game and done it for himself.

This is the page that has his walkthroughs on them...I ccan't link directly to them.
He has Sonic, Boss, and a Emblems guide for Sonic Adventure... Also a complete Sonic Adventure 2... Plus Many more so check it out! Click Here!

All of these walkthroughs were made by Nathan "Segaholic2" Tsui if you want to see the rest to his work... Check out his Site!