Hunters all generally look for the same stats: Agility (Agi), Intelligence (Int), Stamina (Sta), Attack Power (AP), Critical Strike Rating (crit), Hit Rating (hit), Haste, and Armor Penetration (not worth abbreviating). For PVE, a Marksman hunter looks for them in basically this order:
- Hit rating, until you reach 8%; this is about 165 hit rating with 3 points in Focused Aim at 80. This can mostly be ignored till you get past 70, at which point you'll want to start watching more for gear with hit rating. Leveling gear has pretty much none.
- Attack Power, but make sure you watch AP contribution from all sources when comparing gear. You get 1 point of AP per point of Agi (this was nerfed down from 2:1 I think in the 2.0 patch; it was towards the end of Vanilla WoW one way or anther); you should also be getting 1 point of AP per point of Int. If you're looking for a net gain in AP when you switch gear, make sure you calculate for the Agi and Int, as well. Sometimes prioritizing for AP means using pieces with less straight AP and more Agi and Int, because the overall AP gain is larger. Valuing pure AP over Agility is mostly true for gems and enchants; in straight up determination of gear, you'll want to take your crit rating into consideration.
- Agility, since it contributes both AP and crit. While leveling, you may want to value Agi over AP for it's crit contribution.
- Critical Strike Rating, since a Marksman hunter is a crit junkie. You should be getting 10% from talents by the time you get towards the end of the tree, so you're going to want to aim for a minimum of 30% on your character sheet at 80. You'll have more like 12% at around level 50.
- Intelligence, since it contributes AP and mana. You will always be a mana-reliant spec as a Marksman, so don't neglect it. (I used to enchant for it when BM was the favored spec and Int was scarce on hunter gear.)
- Haste, since your goal is 1.5 second cast Steady Shots (they used to be, until they were tweaked to be 2 second casts). The "soft cap" - the point at which you get 1.5 second Steady Shots just from haste contribution from gear - is 522 or 523, however you want to interpret the math. You're probably not going to see haste from gear until you get to Northrend, which is okay - you're probably going to be moving enough that you won't get the full benefit from it until you're doing dungeons regularly. Besides, 5 points in Improved Aspect of the Hawk with the Hawk glyph will more than haste cap you when it procs. Any extra haste just means extra Auto Shots (which is nothing to sneeze at - they add up); hunters' global cooldown can't be shortened from 1.5 seconds.
- Stamina, since it helps keep you and your pet alive. It's not something to ignore, but not something to stack for over things that make you hit harder or faster or more often.
- Armor Penetration, since hunter damage is mitigated so much by armor, isn't something to ignore; it's also not terribly common until you get to Northrend, and not worth stacking in the place of AP/Agi/Int/crit. If you're at the haste cap, you probably would benefit from picking up some armor penetration.
You don't need to worry about Strength or Spirit. If you see gear with Str and Agi on it, it's really meant for a melee DPS class. It's not terrible for you if it's the best you can get at the time, but you'll want to be looking for a way to upgrade to more useful stats. Spirit isn't common enough on hunter gear to be worth stacking, and our out-of-combat mana regen is terrible enough that it's just never going to be feasible to improve through Spi. You can also ignore Spellpower entirely, in all its flavors; it's not going to do anything for us. Spell penetration is similarly pointless (although it may still interact with some trap mechanics, that will eventually be fixed).