Balance is the key to winning in fantasy baseball, however, hitting is less volatile (regarding injuries, etc).
I also think that there's a common misconception to avoid drafting OF early on because there's more of them around. That's true, but you also have to remember the fact that there's more OF positions to be filled on a roster as well. All things considered, if there's a 1B, 3B or an OF available in the second round with equal projections, I'd take the OF for the simple fact that it allows flexibility later on in my draft should I find a 1B or 3B for good value. I know there's the utility spot, and I know I could use the additional 1B or 3B as trade bait, but I don't like drafting with the intention of trading later - yahoo public leagues are notoriously lousy arenas for trading.
It's also key to get a stud SP to anchor your rotation. In a 5x5 league, on average you'll have to come 3rd or 4th in EVERY category, and without a stud SP, it's very difficult to do well in ERA and WHIP. They're also the most difficult categories to catch up in as well.