Proofreading is a process separate from revising. Proofreading is the very last step writers go through to be sure that the text is presentable. Proofreading generally involves minor changes in spelling and punctuation, but it can also include more extensive editing.
It's easiest to approach editing as a multi-step process that starts with paragraphs or sentences in clusters and moves to smaller elements of the text (e.g., commas and apostrophes). If you know you have trouble with some levels of language, plan to leave enough time to edit on that level more than once before you turn the paper in.
Start with Paragraphs; then move to sentences; then focus on words
Check Grammatical Details
Don't Forget Punctuation and Spelling
Commonly confused words
Other errors you know you make
Proofreading is the very last step in preparing a final draft. Just because it's the last step, though, don't assume that it will go quickly. Sometimes you'll need two or more additional "passes" through a paper to be sure you've found all the remaining typographical errors, misplaced pieces of punctuation, or inaccurate words.
A Proofreading Checklist
Proofread a paper several times, never just once while the paper is on the screen or just after you finish typing or writing.
Proofread one sentence at a time, from the end of the paper to the beginning. Look especially for sentence punctuation and any errors you know you often make. By looking at each sentence-because it will be out of context-you'll see more of the punctuation errors and missing words than you will catch by reading from the beginning to the end of the paper.
Proofread once more, looking for problems you know of in your writing. Always make one special reading just for your common flaws and errors.
Read the paper aloud. Sometimes, because you have to read more slowly to read aloud, you'll "hear" problems that you otherwise miss as you read the paper silently. Pay special attention to the sound of words (check for endings) and of sentences (check for sentence fragments and for choppy sentences that should be combined).
Proofread slowly, reading each word from right to left and from bottom to top on the page; in other words, read backwards so that you catch spelling or typing errors. Or read the entire paper from the end to the beginning. By looking at each word-because it will be out of context-you'll see more of the spelling errors than you will catch with your current proofreading process.