If you're doing 25man icc heroics, then I assume you know the basics of your class. I'm not sure what else to tell you besides keep a solid rotation and swap in pieces of dps gear.
Pushing dps as a tank is great as long as you're not hurting the raid more than helping it. I've seen logs where warriors go to extremes just to push their dps/tps and do things like not swap stances to shatter the boss, get bitten early on bql, ask for hysteria, etc. If it's just for fun on an easy boss, then I guess some of those things are ok, but I've seen stuff like that in logs of limited attempt bosses and that's just selfish.