Some decks like to inflict pain. Other decks love to inflict pain. The "Blood and Fire" deck easily falls into the second category. Once you start dealing damage to your opponent, the frenzy begins!
This deck features more than a dozen creatures with the bloodthirst ability. As each of them enters the battlefield, it checks to see if your opponent has been dealt any damage that turn. If so, the creature arrives with some +1/+1 counters on it. So to get the maximum potential out of them, you'll need ways to deal damage to your opponent first.
If you can't deal damage to your opponent, it's okay to cast bloodthirst creatures anyway. A powered-down Duskhunter Bat can still fly over the battlefield to damage your opponent, meaning your next bloodthirst creature will be living large. Be creative about how you enable bloodthirst. Spells like Shock and Incinerate can clear out potential blockers, or they can deal damage directly to your opponent. The 7-power Crumbling Colossus has trample, so it's likely to get some damage through if it attacks. Take any opportunity you can find!
You can finish off the game in a number of ways. Spells like Hideous Visage and Tectonic Rift can leave your opponent unable to block. Warstorm Surge fires off a salvo each time you get a new creature. And if all else fails, just attack with Dragons!
Once you're familiar with the deck, try modifying it. You could add more cards that enable bloodthirst, like Grim Lavamancer or Chandra, the Firebrand. You could also add game-ending creatures with bloodthirst, like Furyborn Hellkite, which has bloodthirst 6, or Bloodlord of Vaasgoth, which has bloodthirst 3 and gives bloodthirst to all your Vampires!