Continuing with the subject of self-editing, the best advice I can give is to read a printed copy of your manuscript. Your mind will pick up flaws you overlook on a computer monitor. When possible, I also read my work out loud.
When looking only for spelling mistakes, you can read lines backwards.You can also read pages out of order so you don't get caught up in the story.
I'm off to Barnes and Noble to do some self-editing myself.