The rules differ depending on where you are and the shows rules. Generally though, amateur rules in the UK don't allow headshots at anytime, the rest of Europe and the USA allow head shots standing, but not on the ground. Submission rules vary aswell, for the most part though, no heel hooks or neck cranks.
Pros get paid aswell.
Chuck Lidell has been giving some interviews for speciliazed magazines and says you're a complete fighter, but he'll knock you out. What do you have to say about that? Babalu - The only blow he'll give are three little ones on the floor.