From: http://tappedout.net/mtg-decks/i-drink-your-milkshake-under-50/
How to Drink Your Opponent's Milkshake:

Overall Strategy: Make your opponent's life your life. The goal is to field life draining threats you can trigger each turn through rally mechanics. The creatures in this deck have been selected for maximum lifelink potential, and ability to trigger rally abilities.

Cornerstone Creatures:

Drana's Emissary: This card is an effective early threat that has synergy while doing nothing. Her flying ability can be problematic for opponents, and triggering rally abilities makes her the most dangerous card in the deck.

Kalastria Healer: A cheap, effective engine for drinking your opponent's milkshake. The potential of the healer is unlocked when you can field 2 or 3 at once and do 6 unanswered damage & gain 6 life by playing 2 Expedition Envoys. Don't swing with these unless you have to.

Lantern Scout: The power of this card is in bestowing lifelink on all your ally creatures. This lets you swing knowing that even if creatures die you benefit from the damage they do.

Rally Triggers:

Expedition Envoy, Kor Castigator, Kor Bladewhirl: cheap threats that trigger rally effects. Kor Bladewhirl also has the benefit of adding first strike, while Kor Castigator has a slight advantage against Eldrazi decks.

Muscle:

Drana, Liberator of Malakir: She earns a spot by being a cheap, flying, first strike ally that buffs other creatures.

Malakir Familiar: not an ally, but synergy with life gain, flying & deathtouch make it a threat capable of defending more important ally creatures.

Bloodbond Vampire: this gains +1/+1 for each Kalastria Healer on the field when you play it, and only grows from there. The lifelink potential here is enormous.

Serene Steward: Like Kalastria Healer this card is meant more to hang back, trigger rally effects, and dispense buffs, but at 2/2 it's a more formidable threat than the healer. She can also function as a mana dump late game.

Tandem Tactics: A good mid game threat since it buffs two creatures (potentially with lifelink) and triggers Bloodbond Vampire's and Malakir Familiar's abilities.

Maintainance:

Vampiric Rites: a good way to trigger Bloodbond Vampire and add some gas late game.

Retreat to Emeria: this card is meant to fix mana flood by turning late game land draws into Allies that trigger rally effects.

Sideboard:

Meant to convert the deck into a more sac oriented strategy if creature removal is problematic during the first game.