As far as the ballpark goes, if you get a park with some sort of "extreme" (i.e. Coors or Tropicana), you need to angle your draft to take advantage of that. A Coors field is a RH hitters park, Tropicana is for the lefties. Choose your pitchers to best counterract those park tendencies, too... If you do get a bandbox, look at pitcher's GB/FB numbers....
Another common mistake is thinking that "closers" are important, like in roto. Any quality pitcher can effectively close a game in PB, so you might do well letting the "big name" relievers go by the wayside, and pick up some of the really good "setup" type guys in middle & later rounds. The most valuable guys in PB are the ones who can pitch a lot and pitch well....
Starting pitching is a real key. If you are lucky enough to have a shot at one of the true "dominators" (Unit, Pedro, Millwood, Hampton, Brown, etc.), do not pass it up. Offense is easier to find in the 5-10 rounds, while good starters are at a premium, so don't be afraid to grab up a couple of real good SP's while the Bagwell's & Jeters go...
The platoon factor on offense can usually allow you to put together a good lineup, but "platooning" pitchers doens't really work.
Also keep track of your AB's at a position.. If a guy only has 450, you are going to need to come up with another 200 or so for that position....
Like real baseball, strong defense up the middle can be a real key, as well. Pay attention to the range & DP values in the infield, and good OF defense will even occasionally treat you to someone pulling a homer back into the park (something I don't think has ever happened with Jose Canseco in your outfield).