Performance Tuning

I started to look into doing some performance tuning of our databases today. I wanted to start by getting some sort of baseline of their urrent state. However I couldn’t seem to find any good information on what to do (for version 9). I found a few links to books to read about it. But no web pages with definitive infomation or scripts. I’ll have to see if my manager will allow me to buy a book on it.