Magazines are rather vital toward the operation of a rifle as they carry a rather large amount of ammo and deliver that ammo into the chamber. Without a clip, your rifle becomes something out of the early 20th century and it is much harder to operate. The stock clip housing is usually fine, but you don't want fine, you want awesome. In order to get awesome you are going to have to modify your rifle, but before you just grab the first thing you find be sure to look over these guides.

Who Made It?
There are a variety of parts manufacturers out there for you to choose from; and while many of them are very reputable, there are some you should look out for when buying. This requires some research on your part and with the internet it is really easy to weed out the bad makers and the good ones. A lot of the time it's personal opinion, but if you notice a lot of people hate a specific brand, take note.

How Much?
You shouldn't over pay for a new part, ever. It can be rather insane to see how much people are willing to pay for a part, but these people are spending their money foolishly. You should make sure you  are getting the best deal possible, and that means having to do some digging. If you are noticing a pattern, you would be right; in every step you need to look something up and that's simply because knowledge is power. 

Make Sure You Can Install It
A lot people buy the part they want and when they get it they have no idea how to install said part. Make sure that you ask someone how to install it and swallow your pride; it's cheaper in the long run.