As a healer, i'll offer some insight in good tanking.
Dodge attacks! Just because you can tank that hit that will wipe out 2/3rds your health and I can heal it back doesn't mean I should have to, latter boss battles get chaotic and I might have to be forced between keeping myself or you alive, and I know I can Quick-cast > Ressurect when you can't.
Don't be a douche! The most douchiest players i've seen happen to be tanks, you get players like NarssicistInChains who think they're amazing tanks because they know all their macros and the basics to tanking, and even if you're the best tank in the world, the entire party is going to grow to resent you if you act like a douche. Though personally, those kinds of tanks have always been the worst i've ever seen, rarely can they keep the hate of more than a single target off the healer, and when the DPS takes the hate to save the healer they throw a fit.