Gnomeaggedon has written up a great guide to something a lot of players (including me) haven't worried about at all in the past: min/maxing your gear before you ever hit level 80. Aside from twinking, there seems to be almost no reason to worry much about gear before you hit the endgame -- you can level in almost anything these days, and by the time you hit 80, you'll replace it all anyway. Why bother? But Gnome makes a good point: he says you should put the minimum of effort in to max out your gear's power. Better gear will help you level faster, will help you play better, and I'll even add that it will help you learn your class better; figuring out early on which stats you want to choose over others will be a big help when you are dealing with all of the epics at level 80. You don't have to spend all your time choosing gear pre-80, as most of it will get replaced with regular quest rewards anyway. But it's good to put some thought into it.
So how's it done? Gnome's posts have some excellent tips on browsing Wowhead for new gear, using Rawr to analyze where your character's at now, and eventually looking ahead to what's next (I'll throw Gear Wishlist in again, simply because that's helped me out a lot). There's so many great tools out there for choosing gear, and it's interesting to note that they're still helpful even pre-80. Taking a second to check your gear while leveling up might actually make that grind that much easier.