Sometimes a writer is asked to offer feedback on someone's work. That may also be the case here. So, allow me to share a few pointers.
FIRST RULE and LAST RULE: Always find something positive to say. No matter how poorly a piece is written, it is possible to find something positive. And don't just make something up. Be honest. I've been editing for nine years, and I've always managed to find something positive. If I can do it (and I'm pretty picky when it comes to the craft), anyone can do it.
1. If you can read, you can give feedback. If you’re not yet aware of all the “rules” for great prose, just tell the person how the piece honestly made you feel. Honesty with tact is the best policy. Give a person the type of feedback that you would like to receive.
2. Be constructive. Say what works about a piece, and what doesn’t work and why. Offer advice or suggestions on how to fix a rough section. Keep in mind, positive comments are just as helpful as negative (have at least one positive comment about a piece and be specific. “Wow, that’s great,” is not helpful).
3. Be objective. If a piece of work isn’t a genre you’d normally read, take this opportunity to open your mind. Ask yourself if the piece holds together well. Do the sequence of events follow a logical pattern, or is it confusing? Look at the writing itself. Is it well written?