Usually.

yesss (or maybe not?) Well before I didn't critize 'cause didn't want my friends to be sad but then my friends are always critizing my art in oder that i can improve > so I began to critize tooo

I would. Well, technically, I already do. I think that it's important to tell your friends if there's something wrong with their art because it helps them grow as an artist as well as gives them trust in you as a critic to tell them when something is wrong. X3

yea but then i feel guilty and so fcking nitpicky even if its good advice TT^TT

Yeah, its constructive criticism (my friends give me that a lot, even though there say I did a good job, they tell me what I might need to improve on).
Its not like you're saying "Your art sucks!" or something.

I'd only do it if they asked. I'm not one to blurt out something wrong with someone's art in person unless they want me to. D:

In the most polite way that I can, yes... Because, I think even if they get mad at me now, in the long run they will benefit from my advice.

No; I think that drawings are-- personal, shall we say? Like, I know my drawings suck, and I wouldn't mind if somebody pointed it out to me flaws if I had asked. But really, if I don't ask, I would get kinda ticked off.
Most of the time, my friends just show me their drawings without asking for comments or critques.
..
That's how I see it anyways. I'm a very independent person (.. at times.. >> ) so I would rather get better on my own, y'know? So treat others how you want to be treated, yo.
</lame>

Yes. I try to be honest and a good critic. But if theres nothing I can really point out I usually just say nicer things.

If they asked.