If you write books you should read books.
If you want to learn to edit better and have your eyes opened to some major flaws in your own stories, you should offer to critique other writers' manuscripts. There's only so much you can learn from books on writing and workshops. Taking time to evaluate someone else's manuscript bridges so much more. It puts you in the editor's seat as well as the reader's.
Finding other writers to exchange work with isn't hard. The dilemma comes in the how to critique for others. What if you're faced with a story you subjectively don't care about? What if you find a rough draft in front of you? What if you can't find anything to edit?
The first thing I recommend remembering is that you are doing the other writer a favor. They need your feedback. They live for the praise but they also need to hear where the problems lie. They want their manuscript to be saleable, to feel confident in sending it out on submission. By reading the work of others and taking the time to analyze it, you'll also be building your editing skills which will help when you revise.
Some guidelines to consider when critiquing:
1) Subdue your subjectivity. It'll still be there and is the essence of you as a reader, but when critiquing for someone else you are trying to help that person out. It's not your job to tell that writer their ideas stink or that they shouldn't write about the subject matter they've chosen. If the subject matter isn't your cup of tea, you can always decline before reading the manuscript or make the focus of your critique the technical aspects. Aim to help the other writer, not attack them.
2) You are not the supreme authority over anyone else's manuscript. You will read and critique the story and then give it back to the writer. That writer may be getting other feedback as well. In the end, it will be the writer's call what feedback to accept and what to decline. Don't get frustrated if you see a later draft and find you were completely ignored. The reasons for this are manifold and I'll write a blog post about them later on.
3) Be on the lookout for the positive as well as the negative. The errors are easy to spot. Don't forget to point out all of the things that please you about the story or the treatment. Writers need to know what they are doing right so they don't start second-guessing themselves.
4) Make sure your criticism is constructive not destructive. Keep sight of your role, a helper. You want to see the other writer succeed. If you come across a place that is confusing or a glaring plot hole make sure you point it out in a way that doesn't say "Boy, you're an idiot." Make suggestions to get the other writer's brainstorming gears turning, but don't expect them to sign you on as the producer of their book.
5) Resist the temptation to rewrite for the other writer. Don't do it. I don't mean switching around a word or two to show better flow. I mean taking whole paragraphs or passages and putting them into your voice. Respect the voice of the writer you are critiquing, even if it's not your style at all. If they need to rewrite something for clarity, point it out, then let them take care of it. They need the growth here, don't deprive them.
6) Be honest. Another big temptation is to gloss over your concerns and give the other writer a friendly pat on the head. Sweet crits are not helpful crits. The writer can get that from their loved ones or friends who know nothing about story construction. If what you've read truly amazes you and you can't find fault with it, point out why. Let the other writer know what you admire about their style or characterizations. Show them that while you don't have anything negative to point out, that you still took the time to really analyze their story. If what you see before you needs the jaws of life, don't be a coward. Point out where the story lost you and recommend major surgery.
Avoid name-calling, derogatory remarks, and the tendency to tear down the other writer. Writing is a personal thing. Feedback shouldn't be. Writers aren't to take feedback personally, and critics shouldn't dish it out in a personal way.
7) Keep in the back of your mind some kind of alert button that can go off when you come across anything that reflects your own weaknesses. Maybe you weren't aware that you over-described your protag's attraction for the new kid at school until you see someone else gush on and on and on. Maybe reading all those dialogue tags will alert you to places in your own story that you need to work on. Maybe you'll see the way another writer handles foreshadowing and mystery in a plot and you'll realize that is something you need to work on.
8) Critiquing takes time, a lot of time. Know what your schedule and patience can handle. If you have a lot of other writers wanting to suck up that time, have the courage to say no if you honestly can't take on another critique. Don't sacrifice all of your writing time. Be sure to keep some for yourself.
Questions, comments, other critiquing pointers you'd like to share? Please do.