Tanking tips and theory?

I was just curious if anyone could write some things on tanking as a Sin. We all do it, I do it, but i'm far from pro. I know how to do things, but I don't always know why things work. I'm curious if someone could explain the best ways of balling. For example, I know your supposed to pull the group after forest in fow to the nook on the right, and some of the casters will walk in, but why? I know that you can use a hill to stack different range mobs, but I don't really know how, or why. I know you can "free-ball" things and sort of walk forward and backwards, or is it sidestepp, and they will slowly ball. Theres all sorts of tricks to balling, and I know about them, but I don't know how to put them into practice and I was wondering if someone could go into depth about them.

http://www.guildwarsguru.com/forum/s...t10476669.html

http://www.guildwarsguru.com/forum/i...t10472883.html