Processor

So, how does one go about choosing a processor? I've decided to build a computer to familiarize myself with hardware, and this is really the one thing I know nothing about. My mobo is AM2, and I'm thinking of getting a dual core. But beyond that, I'm lost. HALP?

>>1
It's never lupus
>>3
Well I am not an "mobo." You have no right to call me that if I made mistakes.  This site should have some rules about harrassments, threats, and name calling.  I am still in the need of more help in that regards