depends on the ballpark I'm building my team around (e.g., if playing at Dodger, I'll look for guys with good 1b/100# compared to RL 1b/100, with speed, and few walks). If I'm at AFC, I look at the HR/100AB# vs. RL HR/100AB and couple that with nice 1b numbers... Really, it's tough to say I weigh just a couple items as you have to build a line up. At AFC, you need a couple of high OBP# guys at the top of the lineup. I sacrifice a lot of power, OPS at Dodger. I also like to use the AVG+ numbers.
Pitching, like jfranco says with the HR/9. I also go with lower walk guys with OAV under .235 at most parks. When it's close, I use ERC# as a tie breaker of sorts (even though that statistic isn't used in the SIM directly, it means something to me). I can usually cobble together some sort of offense around a park, so lean more heavily towards building a strong pitching staff.