In the early game you should try to use your Q to toss him to your turret if he is aggressive, or he has pushed and he and his minions or just outside turret range. Also, try to stand between him and the minions, denying him farm, and hit him with W if he comes close. This works best against meele enemies. To pull red or blue, hit three time, then use W and E. If you get ganked or troble, hit E to slow them, then Q to run away. If you are close to a turret, or some allies, this will save you. Your passive will also help you survive. If you attack someone, make sure to have your passive up, it means you have 30% exstra health. When attacking 1v1 you start with ult if you have it, and just hit him a while you want to save your W for last because it does more damage the less hp the target has. If he turns away, hit E and keep hitting with basic attacks. If he he gets away, hit Q to catch him. When he gets low, use your W to kill him.

You are the tank, and always goes first. When many on your team attacks the same target, Use your W to get the last hit. It's not ks, and you are no support. Also you sort of snowball.
Right before teamfight breaks out, try to use your Q to toss an enemy to your team. If u succeed, the enemy will probably die, and you are 5v4. In teamfights, ult imedialy hit E when standing in the middle. Use W to get last hits when you can. Once you get Thornmail and Warden's Mail, feel free to take on any AD champ, fed or not, even 1v2, because their attack damages them more than you. I met 3 ad champs with a Warmog, Mercury's, Thormail an Randuin's under thier nexus turrets, and left with a triple kill.

Make sure to use your promote whenever possible. Promote plus heart of gold ensures you some exstra gold income, and heal doensn't help that much for a tank while it doensn't do that much persent og your hp anyway, and Voli's passive heals him anyway. In the beginning of early game, use promote on top lane minions, but later, after death or recall, if it's possible, you should send a promoted minion to a lane with no enemy champions, or no champions at all.