It's based on a post I read here, but I also remembered about some feed-back I received myself back when I was a member of peer-to-peer review sites.
Not all feed-back there was awful, and I did receive lots of awesome feed-back that was so great, it really made me think and it showed me things about the screenplays I never saw before. When this happens, it's wonderful. Sometimes it's not, and I apologize if it's too long, these are just a few ideas..:)
1. DON'T TELL ME IT SUCKS. DON'T TELL ME HOW MUCH IT SUCKS.
When I decide to submit a screenplay for feed-back, it's usually because I know there is something wrong with my screenplay. Had I been truly so sure I wrote the best screenplay since these were called scenarios, why bother with seeking feed-back at all?
Wouldn't I just jump in and submit my screenplay to major studios and wonder why I never get any success? So I think when you submit a screenplay for feed-back is like going to a doctor. It's similar in many ways.
Nobody sees a doctor because he/she feels awesome or there is nothing wrong. The same goes when seeking feed-back. And no doctor(I hope) goes around humilliating his patients about how they got into that situation.
I recently watched a show about people who had serious weight problems and needed to see a doctor. But the doctor didn't belittle them or humilliated them or told them:"You look like shit! You eat like a pig, you filthy bastard! What did you expect?".
No, he was more like:"Ok, let's see what we can do. I think you should lose some weight, you need to follow this diet and we'll see if you need surgery".
Same goes for a dentist. I've been to a dentist and he didn't come across as arrogant or scolded me about the state-of-mouth. He was(like the show doctor) more like:"Ok, we need to fill this cavity, this tooth needs an extraction. This one can still be saved, but might need some filling later on, etc.".
Same for screenwriting review. Give competent advice, critique if need be, but always treat the writer with respect. Always remember that behind the screenplay you received, there was a writer who tried his best, but still needs to do some work. So don't tell them it sucks. Rather, tell them why does it suck and how to make it better.
I don't know about you, but if I ever come across a doctor who starts to insult me and really give a harsh review of my condition and how I got there, I would do my best to never see him/her again!
2. NEVER GET PERSONAL. NO PERSONAL QUESTIONS.
This one happened and it's usually related to the first one. "What do you do for a living, I hope it's not writing?", or "You need to either improve your writing really fast or find a non-writing job asap". Hold on a sec, who are you exactly? We're not friends. This isn't a date.
So what's with these questions? You don't ask them because you care about me, you ask them to support your oppinions or confirm biases. Unless I come forward and give you really personal details, you have no right to ask. Not unless we become close friends. And never make assumptions.