For future reference start of by reading the stickys:
http://forumserver.twoplustwo.com/45...-first-772011/
Differenece in aggression stats is explained in the HEM FAQ:
http://faq.holdemmanager.com/questio...ons#aggression
Personally I believe agg factor is pretty useless for NL and if you are going to use an aggression stat then use %.
As a rough guide for NL 6 max I would say < 24% is passive, 33%+ is pretty agg and 40%+ is verg agg. If you do a search I'm sure you'll find several articles on what you want.