This article is for those who has been in photography before, and want to take next step as cosplay photographer.
As starting point, go to a con (cosplay conference). Cons are the best place to start cosplay photography as they have a ton of cosplayers. most cosplayers go to cons to get their pictures taken, so this means you have a ton of willing models. Depending on the scenery of the con, you might be able to get some amazing shots.
Be polite, ask before you shoot, don't gank another photographers subject matter until they are done and you'll be on your way.
Most of the shots of cosplayers at cons are snapshots taken in hallways. Although most people will give you 3-5 minutes, it's polite to only take 4-5 shots. They're dashing from panel to dealers room and eating pocky and hitting people with yaoi paddles so getting a more involved shoot from a complete stranger is a lot harder to get - if that's the sort of thing you're interested in doing with cosplay photography.
If you have friends who cosplay and would be willing to do some shoots for you, that's always an option. and if you cosplay too you could do some self-portraits.
Just put in mind that there's no 'wrong' way to photograph cosplay (except perhaps as a fetish/freak hobby or with lots of the upskirt stuff that makes costume secondary).
Watch this youtube video provides some basic information on etiquette and ideas.