The simplest way to critique I think I can manage - think of three good things about the work and one thing that can do with imrpovement - and give positive feedback on how it may be improved. Not "the characterisation is bad" but "I think the character of David could be developed with a little more back story".

The more complicated critiquing advice goes as follows:

Giving criticism

"What I had to face, the very bitter lesson that everyone who wants to write has got to learn, was that a thing may in itself be the finest piece of writing one has ever done, and yet have absolutely no place in the manuscript one hopes to publish."
Thomas Wolfe

1. An easy way to start is to agree to say 'one good thing and one bad thing' about a piece of writing. Nobody should be allowed to get away with not saying a bad thing. Are we all so perfect that there is no room for improvement?!

2. Have confidence in your own opinions. Don't think: 'It's my fault that I don't know what this person's poem is about. I suppose I'm just too stupid." Ask questions about it. Point out specific things which confuse you: "I don't quite see how the end of the poem links up with the beginning". Make sure you also point out something you like, however small. "I enjoyed the way you describe the colour red in the third stanza."

3. You don't have to give feedback on every single piece that's posted in the workshop, but sometimes you might ask yourself why is it that you never respond to X's work and always to Y's? You could find some interesting answers there.

4. Don't be intimidated by people with more technical knowledge than you. If their website is slow to load on your computer, then feel free to say so. If there are images missing, tell them. Don't just assume your machine is at fault. If you're on a course which involves html or any other kind of programming, debugging will be a natural part of what you do when you give feedback to fellow students on their sites. That kind of help can be invaluable so don't be afraid to draw attention to such problems.

5. Polish up your critical vocabulary. Sometimes it's hard to find the right words to usefully convey what you're thinking. You might need to stretch yourself to find the best way to explain your thoughts.

6. Finally - when you receive criticism that is particularly helpful, ask yourself what makes it work so well. Perhaps you could employ the same techniques when you are required to give feedback. Or perhaps not all techniques are suitable for all people...

Receiving criticism

"Fortunately both my wife and my mother-in-law seem to love digging up mistakes in spelling, punctuation etc. I can hear them in the next room laughing at me."

Sherwood Anderson

1. Criticism is scary. The word has very negative connotations and yet it has so many positive uses too. Many of our fears go right back to childhood, and it's helpful to try to locate the particular sources of your own worries relating to being criticised. It can bring out a real panic response in people, producing blushes, sweating, trembling, increased heart-rate... you might find that you are so nervous that you cannot properly comprehend what is being said. Work on this. Separate that childhood fear from your professional role as a writer.

2. Try to be honest with yourself and your fellow students about what you really want from criticism. Maybe you just want to receive fulsome admiration, but they won't be doing you any favours if that's all you get. Move beyond the pat on the back and think about what you really want to know - is my plot realistic? is this character believable? is this language too simple? If you get answers for those questions and admiration, then you're doing pretty well!

3. Once you've decided what level of feedback you want, make sure you're clear about it to your readers. If you simply want gentle support and a few corrections, say so. If you want rigorous no-holds-barred editing - tell them. If you're ambiguous in stating your needs, then don't be surprised if you get the wrong kind of response.

4. Don't offer up everything for feedback. Be selective and only request criticism when there is a clear reason to do so. Know what you want and ask for it. Don't post a piece which you know is full of problems - people will generously waste their time telling you things you already knew anyway.

5. Be realistic. A poem scribbled on the bus last night is going to be less polished than one which has been redrafted ten times in the last six months - therefore it may show more faults (but not, of course, necessarily - this is the problem with the Muse!).

6. Don't be upset if your reader gets completely the wrong end of the stick.
Writing is a two-way process, and texts are open to many different interpretations. The best way to control interpretation is to make your writing as precise as possible, but even then your work could be misconstrued. Don't take it to heart, but do check whether you have communicated as well as you possibly could.

7. You might want to be selective about who you ask for feedback. If you're working in a particular genre, it would make sense to show it to another writer in the course who is writing in a similar genre, eg poetry; romance; children's. Writers writing in other genres could provide some useful feedback but maybe not as much as someone who knows the genre.

8. Look back again at 1. At all times, separate your self-esteem from your writing.