The role of a vanguard is to go into the team fight slightly ahead of your team mates, You provide initial damage and a distraction for your pure DPS team mates to come in and mop up the enemy. Until you get warmog's Armor you'll be very squishy. I suggest getting vampiric scepter, boots of speed, then a dagger. Upgrade your vampiric scepter to the amulet then start getting warmog's armor and complete it. Next go for boots of lucidity, then finish up your starks fervor. Last core item you get is black cleaver, after that if the game is still on hit sheen then transform to trinity force. This late in the game The Brutalizer is more effective than the avarice blade, but either way the last item you'll get is the ghostblade. I suggest switching it's location with the boots so you can just press 2 to activate it.

However even after you have the whole build done you'll still need to watch your HPs and when you get a little low, retreat a little to lure your opponent further away from safety so your team can save you. With the life steal, max hps, hps regen, and atk speed in this build you'll find it really easy to get back to full hps by attacking troops or hitting up the jungle. Using this play style can pen down the enemy champions as your team goes back for hps or waits to be reborn you can harass and keep them from pushing the lanes. So when your team comes back the enemy hasn't turned the tides. Remember this isn't a tank build, so even though your tough it's best to dive in and out of the team fight whenever you get focused and you'll be doing enough damage that they will focus you.

If you do this too well the enemy will run when they see you, so if this happens don't chase leave the lane for the jungle kill some stuff then go back in from behind you can use your transformation to drag the enemy further from safety, this gives you and your team mates more time to kill them before they escape.