Don't Go Looking For Problems

The biggest problem I have with editing is becoming overzealous.  As I've said about editing my own, "When I'm in editing mode, I want to edit. If I go through a page and have no changes to make, I feel like I'm missing something."  This also happens when editing the works of others.

If I was a beginning editor or looking at the work of a beginning writer, it might be acceptable.  But in general, it causes more problems than it solves.  Sometimes there isn't a problem.  Sometimes you find something that could be changed, but that doesn't mean it should be changed, let alone that it needs to be changed.

The usual advice is to use a light touch.  Don't be picky.  Find the biggest errors, fix those, and don't worry yourself about the little things.  It's not bad advice, but I would put it in a different way.

Don't go looking for problems.  Read the writing like you were a generic audience member.  Every time something makes you stumble or read twice, that's a problem to fix.  If it's smooth from top to bottom, then you've got a great start.

It may be a good idea to do a second reading that is more nit picky, but remember that you have already read it and it's smooth, so you don't have to worry about anything other than the meaning of the content and the mechanics like spelling and punctuation.