If I were a pathological liar, I would tell you that copy editing is when you clone yourself, manipulate your genetics, then step back and see the effect it has on your double. But, I’m not. And we’re not even up to that point yet (i.e. cloning humans). But, you should still know how to copy edit.
Strategy #1 CUPS!
CUPS is an acronym that goes like this:
C – capitalization
U – usage
P – punctuation
S – spelling
This method encourages a series of passes rather than edits by the reader, and usually works by writing CUPS vertically in the top right hand side of your first page. Once you completed one step, you write your initials as to not forget you checked that. This works good in elementary classrooms, but this will work just as good for you.
As extra resources, I always recommend the Purdue OWL. They have a lot of good resources on nearly anything and everything style- and grammar-wise.
And, if you want to act as editor, don’t forget to know all the secret symbols of the copy editors’ society. (There’s no secret society, but there is common symbols that editors will use to speed up the process, reminiscent of a time when everything was on paper and not the computer.)