If you really need something proof-read, you should ideally have someone else do it. However, there are times when this is simply not possible, and you'll need to do it yourself. There are some simple tips that you can follow in order to make sure that your proof-reading is fool proof.
You should give yourself some time between finishing your paper and proof-reading it. That will make it more likely that you'll spot any errors that you made.
You should also read it aloud. Sometimes things sound very different out loud than they do when you read them silently, and you can catch mistakes in wording much more easily that way.
Also, make sure you leave yourself enough time to proof-read properly and try to see yourself in the shoes of your audience. The more you can role-play and really think about what you're doing with the paper, the more likely you'll be to determine how good the paper really is and what changes should be made.