Self-Editing Tip: Proofreading your work in different mediums and on different devices can help you catch errors you missed.
This is a quick and easy tip that makes a BIG difference. 
Changing the doc or file format before you proofread your work will help you notice things you might miss otherwise.
If you normally read your manuscript on your computer, try reading it on your e-reader or printing out a hard copy instead.
Even something as simple as changing the font and/or text color can make those sneaky little typos and errors easier to spot. 