How to Give Helpful Feedback
Be Honest and Positive
Going back to an earlier post, the best feedback to give and recieve is both Honest and Positive. Again, hat tip to Darren Groth for combining these.
To everybody who I critiqued before I learned about the positive portion, I apologize. I assumed you would know that I liked it or felt somewhat positively about it if I didn't say anything. But that's not how that works. And I wasn't receiving positive critiques myself at that time. During that time is when I had an honest = brutal CP and people giving me 1* reviews as though they were being helpful. I was not intentionally being unkind, mean, or nasty. But I wasn't highlighting the things I liked frequently unless I really liked them.
It's important to be both honest and positive. This will make sure no one feels like you're dishonest about either the positive things or the things you see need improvement. The writer is benefited in that they have actionable feedback and won't end up delusional about their own work.
Use the format agreed upon by both parties
Learn to write a dev edit letter. This is the first way writers will get feedback from editors and getting it early on from beta readers and critique partners will get them used to this format. It also gives you practice developmental editing, which will only improve your own work if you are a writer. If the writer has sent you a list of questions, use the letter to answer the questions. If you have overall statements to make about the manuscript or story, use a dev edit letter to make those statements. However, before sending a dev edit letter, make sure the writer is open to getting it.
Make sure they know ahead of time you'll be commenting and/or editing so that they know to expect the comments or edits. This doesn't mean sending them a message right when you start, but if the agreed-upon format is a dev letter, and all of a sudden comments are flying into their inbox or throughout a returned MS, the writer is rightfully mistrustful and possibly taken aback.
Are you both verbal/audio communicators and learners? Then have a phone call or a video chat! I, for one, cannot retain anything said over the phone to me. I have some issues with my ears and I have to be in a specific environment free of any other humans or higher cognitive distractions to listen to something I need to learn from. I need to be able to take notes. I cannot take notes on a phone call. I do a little better over video chat. In-person is easy because the person sees me taking notes and will pause.
A writer should learn to get used to the workshop format used in many group settings, but make sure it's something you agree upon if you are just you and the writer.
Ask Questions and Be Descriptive; Don't be Prescriptive
Describe your reactions or ask questions. If something is funny or you enjoy it, by all means, point it out! But if something doesn't work for you, don't try to fix it. Ask a question to get their writerly brains going. Describe your reaction - even if it's just a "this isn't working for me."
But don't prescribe a correction. I couldn't find a positive framing for this. But overall, I've gone awry when giving prescriptive feedback. That's entirely the reason I got pushback on feedback I gave a writer. It was prescriptive (and wrong.) Your feedback will be equally useless when being prescriptive unless you've already established a relationship where your prescriptiveness is trusted by the writer.
Mary Robinette Kowal's Feedback Guide:
I'm going to end with MRK's excellent feedback guide. This is a start. The discussion of how to give good feedback should go much deeper than this.
Writer of spec fic.