Voice your concerns politely and pleasantly. If the annoying coworker happens to be your office mate--who just happens to be chatting loudly on the phone on a personal call while you try to respond to company emails, simply say that you'd like her to lower her voice so you can concentrate. Jokingly blame your poor attention span on the request--self-deprecation is a little sugar to make the medicine go down.

Take the matter to the authorities if your polite requests don't do the trick. You can warn him first--tell him that if he's not able to better organize his papers so that half of them aren't taking up your desk space, you'll need to tell your supervisor about this problem. The warning might work, but if not, get Human Resources or your manager involved.

Transfer departments or find a new job if this annoying coworker truly makes life at the office unbearable. But keep in mind that this is a last resort--and that the new office might contain its share of annoying coworkers as well.

Consider whether you have unrealistic expectations of your coworker. While some employees truly are disruptive because of their annoying behaviors, sometimes you just need to be more accepting. For all you know, your coworkers could find some of your habits annoying.