Gloves are as personal a piece of equipment as your helmet and ice skates. For this reason, you should buy your gloves new. Hockey gloves are usually leather (or leather-like) in the palm, and protective padding on the knuckle-side of your hand. Like helmets, you would do yourself a favor by trying out these out in a store, so you can ensure a good fit.
Some gloves have a tremendous amount of protective padding, and others are more sparse. Consider also the weight of the gloves, as you want something that isn't too heavy.
Another thing to figure out is the feel of the stick when you're wearing the gloves. It's illegal to manipulate your stick with your bare hands, by cutting open any part of your glove, so make sure the palm is flexible enough for you to form a good grip on the stick. With regular wear and tear, the glove becomes more "loose", so don't let the new feel fool you.
Gloves get battered a lot during a season, and the material covering the palm sometimes becomes very worn and disintegrates (not to mention smelly). I've met players who restitch these back to the rest of the glove, or patch them up. I've definitely seen duct tape repairs to gloves, but when they're that far gone, used it as an excuse to buy a new pair.