Youve got huge MS use it well. You can knock you enemies in your team with your E. Q is your main damaging spell early game its one of the best AoE spells. Your W provides a huge survivability bonus. Use your R allways during a teamfight cus of its AoE CC like Jack in a Box it will disrupt your enemies and reposition them like Gragis R :D
Summ spells Ghost and Clar why clar cus youve got massive MS if you scout some1 it will be easy to hunt em down no matter where they are.

Your role is to push the enemies carry into your team and then use Omen to slow him down so your team can kill it more quickly everything after is not important cus a team without a carry is like a fish on land it will vanqush. Tanks dont need tons of HP/AR/MR they need just a bit more than avarage to do their role in a team fight. Rush for Omen its one of the most important items for a tank i dunno why ppl aint takeing it. It changes the flow of a team fight.

Start at red buff then the wraiths after that wolves and then blue you shoud have your smite by then. After you can eider gank some1 or continue jungling to lvl 5 and then go gank it will be alot easier. After the laning phase join team fights go direct or ambush from the jungle its on you to make a choice. Ward some places (Find a warding guide on this site or sth). Counter jungling is easy escapeing a gank as well youve have much MS use it.

This is pretty much it. How to play him positioning... Check it on you tube some random commentary or sth I dunno use your brain!