I did this last year, and it turned out terribly. But I still believe it should perform about as well as most experts' complicated previews and predictions, so I'll try it again. Heads for the team that has home-field advantage (or would if that series were to happen), tails for the other. As a new twist this year, I'm consulting Random.org for a number between 3 and 5 or 4 and 7 to tell you how many games each series will take.
The expert this morning is a 2001 penny I found in my desk drawer. Minted in Denver, so expect some anti-Giants bias:
ALDS: Rays over Rangers in 5; Yankees over Twins in 3 (damn penny/randomizer!)
NLDS: Phillies over Reds in 4; Giants over Braves in 3
ALCS: Rays over Yankees in 5
NLCS: Phillies over Giants in 4
World Series: Phillies over Rays in 5
That was a lot of heads; tails came up only once, and at the worst possible time for me, kittens and puppies, and the light side of the Force. Looks about as good a guess as any, though.