What is the Blogging from A to Z challenge and where can I find more participants? Right here.

Reading out loud is one of the best way to catch errors. This may seem awkward if you aren't a reading out loud person or don't have a private spot to go hang out and talk to yourself, but there are ways around it.
When you read in your head your eyes will often skip over errors, especially if you wrote the words. You know what you meant. You've read these words probably half a dozen (or likely a lot more) times and you know the story. You may even find yourself skimming along to get to that favorite scene. None of these are helpful in catching missing or wrong words, repeated words, awkward phrasing, and choppy or massive run on sentences.
You can catch all this and more by reading out loud! (I feel an infomercial coming on.)
Will it help catch everything? No, but it's a big step toward the polishing for submissions or self-publishing. I wait to do this step until I'm done incorporating feedback from beta/critique and have moved past tweaking. So around the last step before submissions, a paid editor and/or preparing to self publish.
I find it works best to get out of whatever program I wrote in and work from a printed copy. Cheap like me and hate wasting paper? Print it in a small font, single spaced, two sheets to page an use the back side too. No one is going to see this but you. As long as you have room to highlight errors or scribble notes in the margins, that's really all you need.
Now, you could read this printed copy yourself, making note as you go. Maybe that will work for you just fine. I've tried it. I find I still fall into the problem of knowing what I mean rather than listening to the words I'm saying.
What works wonders for me is having someone else read it, specifically my computer. It can't skip anything and all the flaws in phrasing and sentence flow are abundantly clear in that computer voice. I currently use Word with the Windows Narrator to read for me, but any program that will read for you works. I put in my earbuds and sit at my desk (one of the few times I leave my comfy chair for writing) with my printed copy and have at it.
This may seem like a long process, but it really does catch so much more than eyeballs alone. I highly recommend taking the time and effort to listen to your own book.
Have you tried this and if so, did you find it helpful?