All of the possible deck commanders are listed in the sideboard. Gotta know who you're playing against and choose your commander accordingly. Tsabo Tavoc is great for people who rely on their commander, Rakdos is great for pumping the critters out, Kaervek is so powerful (that you will be instantly targeted by everyone), and Olivia is probably my first choice--she's a cheap flyer that grows while removing other creatures or taking control of them.
Rakdos style: go nuts with big creatures, cause lots of damage, and don't worry if your creatures end up in the grave yard.
Bring them back with:
Aphetto Dredging, disturbed burial, profane command, death denied, haunted crossroads, phyrexian reclamation, and nim deathmantle.
Use small and persistent creatures that have death touch/indestructibility/regenerate to stall for the first 4 turns or so while you get ready to put huge nasties on the field:
Darksteel Myr, Darksteel Sentinel, Dark Imposter, Vampire Nighthawk, Thrill-Kill Assassin, Shambling Remains, Reassembling Skeleton, Nikiria Cutthroat, Escaped Null, Firewing Phoenix, Dark Revenant, Baleful Eidolon
Use board clearers to destroy lots of stuff:
disaster radius, plague boiler, necrotic plague, shriveling rot (in the middle of an unsuspecting combat phase), comet storm, and hex
Curse your opponents/steal their creatures with:
Lim Dul, Polluted Bonds, Grave Betrayal, Curse of bloodletting, Painful Quandry, Olivia Voldaren, Sepulchral Primordial, and Nezume Graverobber
For style points, finish the game with a HUGE nasty spell:
Grimorie of the Dead, Insurrection, or Colossus of Akros (monstrous of course).
When in doubt rely on exsanguinate--it's your permanent new best friend.