Be sure first that you have a great amount of knowledge or experiences with punctuations and grammars before proofreading. But if you know what is right, then go on, but if not, then proofreading won't be a use at all.
1. Keep yourself from getting distracted, focus. Look for a quiet place to proofread where it is far from all the disturbances to help you focus.
2. Don't read the piece silently. Hearing can be sometimes the best judge with grammatical errors and sentence constructions.
3. Try to be a little soft on yourself while on the job, taking little breaks won't hurt, but instead will help you calm and set your mind back to regain your focus, for sometimes doing something too long makes you lose your focus.
4. Put in mind that this is not just about grammars and spellings. Styles can also be a great factor, and having inconsistency in style can be a great downfall. Make sure that your style is consistent, like your headings having all the same font style and size. Do this line by line, and use objects like rulers to guide your eyes to avoid skipping of lines.
5. Word by word it is, you need to practice to read sentences or paragraphs word by word with great focus. Normally, when people read they tend to just slide through the lines, which can make us not notice some small errors. Generally, most of us rely on our not so accurate peripheral vision for most of us can only focus on six letters in one stare. Effort is needed, just for a short period of time, make everything around you go slow and proofread slowly word by word, letter by letter.
6. Take a little break, and don't proofread after writing immediately. Again, focusing on something for a long time takes our focus away. So it'd be best to proofread after taking a little break to have a refreshed mind, and be able to read a document as if you've never seen it before.
7. Proofreading on screen only is not advisable, true that you'll be able to pick up some mistakes while reading it on screen and revising can be easier, but everything just can't be spotted at once. So make sure to do another proofread with a hard copy of the document/text.
8. Our minds can be sometimes bias when it comes to our own works, so to be more assured, reread your paper many times and you might spot one more mistake.
9. Ask help from another professional proofreader if you are not sure with your work. They will help you to complete your work faster and error-free.
10. Research more about proofreading tips, it might give you good ideas so you can continue working effectively. Also enrich your knowledge about proofreading by reading academic books, thesis, news. These materials are very strict with grammar and spelling so they might condition your mind with perfectionism once you are exposed to these materials.