Editing can be a tricky beast, but here are a few tips to help you when you're writing and self-editing:
1. Write without editing. It's always easier to cut than to add in, and you'll find writing to be more enjoyable when you aren't nit-picking every last word.
2. Let your work sit for as long as possible. It's hard to "objectively" edit something when it's still fresh in your mind.
3. Print it out. There is something about editing on paper that makes the process more enjoyable...and your eyes will thank you for it.
4. Don't be afraid to "kill your darlings," as Stephen King puts it. Don't fall so in love with your work that you aren't willing to make it better.
5. Read aloud. When you're finally ready to proofread, read your work aloud and touch each word with your pen as you say it. This helps you maintain focus and not skip words with your eyes. I've also recently been experimenting with the MS Word "speak" feature. After I do all of these steps, I then have the computer read it to me, and I listen for errors.
That's it for tonight. Happy editing!