If you've never done an RGD draft before, I highly recommend drafting Red/Green/Blue. After I wrote the article that Oversoul linked, I tried forcing myself into those three colors and had much better success than before.
Basically, in the first pack, you want to take all the best green, red and blue cards you can. Look for mana fixers (Farseek, Civic Wayfinder) and beefy creatures (Seige Wurm, Bramble Elemental) in green, removal (Fiery Conclusion, Galvanic Arc) in red and flyers (Snapping Drake) in blue.
In the second pack, take the best Gruul or Izzet cards. Or any good mono-colored cards, as well. Repeal, Steamcore Weird, Ghor-Clan Savage, Silhana Ledgewalker, Silhana Starfletcher, Wildsize, Pyromatics, Izzet Chronarch, Wee Dragonauts, Scab-Clan Mauler, and Streetbreaker Wurm are all great commons from the set. Especially Wee Dragonauts, which I think are vastly underrated. Also, look out for bloodthirst creatures, since they'll combo well with the third pack...
Where you go for Simic. Simic Guildmage is absolutely nuts if you can get it, but it's uncommon, so it doesn't come up too often. Good commons include Helium Squirter, Silkwing Scout, Simic Ragwurm, Sporeback Troll, Seal of Fire, Cackling Flames, and Coiling Oracle. Assault Zeppelid is one of the best commons you can get. If good graft creatures present themselves, try to pick up as many as possible. It's a powerful mechanic.
And that's my suggestion. Also, try to pick up the common dual lands as early as the 3rd - 4th pick. They really help your mana base a lot.