Lots of good suggestions above. Especially true is that it is very very difficult to proofread your own work. A bit easier if you've let it sit awhile, but you'll still only see (especially as regards to interpreting type specs, etc.) what you saw the first time.

Depends, too, on what you are proofreading for. Your document needs to be read several times -- once for each thing you're looking for. Such as once word for word with your original copy to ensure everything is there and spelled and punctuated correctly, second for sense and to catch awkard wording, grammatical errors, etc. and another time for adherence to type specs, hyphention (bad breaks or too many in a row), rag, etc.

Words Into Type is another good reference for USers.

If you're proofing your own work, Spell Check can be useful but you have to recognize that it can only catch some slips of the keyboard and you actually have to engage your brain when using it (and ignore most of its suggestions).

Linn