If you mean the party that makes the game easiest, I would have to say 3 Mages + Sword/Shield Warrior to tank.
But plenty of other set ups work just fine. Generally you'll want at least one mage (specced for healing and crowd control) and a tank. I'm sure there are plenty of set ups you can get to work with varying degrees of micromanagement. --- If all else fails, use fire. PSN - cynicalsaint ~:::~ XBL - cynicalsaint0
Shale is much better at holding aggro than Alistair, and his hit point buffer makes him a better tank until Alistair gets into massive armor. Consider swapping Alistair back into the tank role later in the game.
Sten, Oghren, Dog, and Shale all make good DPS warriors. Oghren gets a slight edge here for comedy effect.
Zevran starts with no lockpicking skills, and Leliana has hawt accent. Honestly, thought, I'm not really fond of either of them, so I would make my PC the rogue in this party.
Spirit Healer > Shapeshifter. But go with Morrigan for sex appeal and/or less preachiness, if desired.