LOL you have much to learn young grasshopper. The only 'rule' for want of a better word is 'if it harms none do what you will.' Really how many rules do you need? It's hard enough keeping just that one. Besides, it does pretty much conver all bases. It's near impossible to generalise about paganism, as it's really an umbrella term and the practises are so varied between people. That's the closest you'll get to a general consensus (Though to split hairs it's wiccan/eclectic) Of course other traditions/practises (e.g Druids) have their own specific codes of conduct. I personally live by a lot of Buddhist ethics, was doing that anyway without realising and they mesh pretty well with paganism. Others follow prescribed ethics from a whole mass of other sources. Ah the joys of being eclectic.
Though that is a good "rule" to live by, it is only mandotory for Wiccans. It came from the Wiccan Rede, but has been adopted by many pagans as a way of life. Personally I prefer Aleister Crowley's "Do what thou wilt, be it the whole of the law."
"If it harms none..." is the real challenge of the Wiccan Rede. To do it right, you've got to really think things through and communicate with all people who will be affected by your actions. I've been accused of being "politically correct" because I do what I can to avoid being misunderstood and ticking people off. There are certain words that are not in my vocabulary for that reason. However, it's not political correctness so much as an attempt at good manners and good karma.
To be honest, the only defanition that I think you can give to all pagans is that they're almost all nature-based religions..
