The #1 thing that I think will help people improve their notes is:

Justify them. Explain why you're giving the note you're giving.

There are so many times I get notes that are just someone explaining a rule they heard without understanding it

or

someone giving me a note that I don't understand because they don't tell me why they're giving it.

It's okay to say things like "This isn't working for me", but it's helpful if you say "This isn't working for me because I don't feel the payoff is earned" or "This isn't working for me because I don't care about the character" or something. The worst is "Don't do X" with no other comment or explanation. Most of the time it feels like the note giver is just looking for things to pick at just to do it.

Also, from the note-givers perspective, it helps you immensely to think for a second why something doesn't work. I mean, maybe you ARE just repeating a rule without understanding it! We've all done it. Maybe figuring out that not giving enough time to a relationship development makes it fall flat-- figuring that out can help you, as a writer, too.

(this, too, isn't a one-size fits all rule, though. Sometimes you just need to say "This part is confusing" because it is confusing. Or whatever. And sometimes the author may disagree with your reasoning, that's fine too. They may think well, you say this is boring because it's a tangent, but I bet it's actually because I haven't won you over to the character's side yet)