Warcraft has it's own version of Ebay, The Auction House. After you accumulate silver and gold, you can drop in and bid on weapon and armor upgrades, and even things like cats and parrots.
You can also sell those things you don't need, or that you acquired from whomping monsters.
I never concentrated much on a weapon, being primarily a spell caster, but yesterday I picked up this staff. I was surprised how big a difference it made. When the monsters broke my root spell and charged in, it helped a lot to be able to take them down with a couple of whacks.
The staff in the picture is a Dwarven Magestaff of the Wolf. In addition to more clobbering power, it gave a big boost to intellect and spirit, both useful attributes for someone who spends a lot of time tossing spells.
Of course, as I mentioned before, upgrades may boost attributes, but at the same time they can also look really bad. What's with those gloves?