I've been thinking about this question for a while now and have asked a few of my friends what they've thought about it.
It's very simple: In a perfect world, who would be the 10 playoff teams? Basically, all you have to do is pick a winner of each division and two wild card teams. No need to go any further into it than that. No need to pick who the teams would face in the divisional series or who would win. Just pick the teams that would make it, and maybe give a brief explanation for why you chose them.
Simple enough, right?
AL West: A's - Pretty obvious pick there.
AL East: Rays - Always had a soft spot for them. I see a lot of similarities between them and the A's: A small-market team in a poor stadium with a small but dedicated fanbase that is often looked down upon.
AL Wild Card: Mariners and Orioles - I've never had anything against the Mariners, and I really liked my trip to Safeco. I don't mind them at all. As for the Orioles, I have lots of family in Baltimore and I find them to be a fun team to watch with a good fanbase (40,000 chanting "You Suck" at the Yankees can't be wrong!).
NL West: Diamondbacks - I already liked them when they had Cahill and Ziegler, and I love Paul Goldschmidt because he dominates San Francisco. Adding Pennington made me pull for them a bit more and now they have BMac, and who doesn't want to see him do well?
NL Central: Brewers - Not sure why but I've always had a thing for Milwaukee.
NL East: Nationals - Before they had Gio I liked them but since he got traded I've really been pulling for them.
NL Wild Card: Padres and Phillies - San Diego is another small-market team that hates the Giants and I like all of the Philly teams. I was also considering the Reds and Cardinals, I've always liked them a bit as well.
Those explanations were a bit more lengthy than they need to be but you get the point.