A quick note before you get started on reading. This is a guide to critique, WHEN you want to give it (or when people ask for it). I'm not saying that every singly comment you leave must be deep and meaningful or that it's never ok to add something to a collection without leaving a comment. It's up to you to decided when to critique something or what kind of comment you want to leave.
A (RATHER OPINIONATED) GUIDE TO CONSTRUCTIVE CRITIQUE Version 2.0
* If you don't know what you're talking about, then don't talk about it! Seriously. If you've never taken an artistic photograph in your life then while you are more than qualified to give your perception of a piece of photographic art, you probably shouldn't start telling the photographer how to improve their work. Because you DON'T KNOW! If you've never drawn anything in your life and have never studied drawing or learned anything about it, then don't tell people how they should draw things 'better'. Because you DON'T KNOW! By all means tell people how their work makes you feel, what it reminds you of, what mood it puts you in, whatever...but if you really don't have a clue about the processes that went into creating the work, then don't comment on that aspect of it.
Update, October 2011: For the people who say that you don't need to know what you're talking about to know if you like or dislike something, you're quite right. Anyone can tell if they like or dislike food, but chances are an experienced chef will be a whole lot better at suggesting exactly what ingredients in what quantities will improve it effectively.
* Say HOW you think something can be improved. There are very few things more annoying than "You should work on the lighting". How? What's wrong with it? What needs work? WHY does it need work? How should it be worked on? What advantage would there be to doing it differently and how would this increase the effectiveness of the overall image? If you don't know the answers to those questions or can't explain your thoughts eloquently and in an informed manner, then don't waste your time with "You should work on..." or "The (whatever) could be better" comments.
* Say what you DO like. Even if you don't feel that you're in a position to give constructive critique on a piece, you can still say what you DO like about it. Try not to stop at "Good job!" or "Nice work!". WHY is it a good job? WHY is it nice work? Explain yourself! I can only speak for myself, but when someone likes a piece of my work I like to know why. I like to understand what makes a person appreciate something. It's not hard to leave a comment explaining this...you KNOW why you like something when you look at it. Just say it! The artist will appreciate you taking the time.
* If you like something enough to fav it, then you ought to be able to leave a comment. In my humble opinion, there is nothing creepier than someone faving half my gallery and saying absolutely nothing at all about any of the pieces of work that they'd fav'd. If the person doesn't speak English, then fair enough. Or if you really like something and don't have time to comment when you first see it, fair enough. But apart from that there is NO excuse for massive faving sprees and no comments at all. It makes you look like a desperate attention-whore, and no-one likes that.
Update, October 2011: This tutorial was written when dA was a considerably smaller environment, long before Groups happened. As the site and our galleries have grown, it becomes more understandable that there isn't always time to comment on every single thing you look at or like.
* Remember that not everyone WANTS your 'help'. If someone has set their preference to 'Critique Discouraged' then respect their wishes - don't tell them how you think they should be doing things 'better' If they wanted to know what you think is wrong with their work, they'd have set their preference to 'Allow Comments' or 'Encourage Advanced Critique' . It is important to remember that even when people have their preference to set 'Allow Comments' it doesn't necessarily mean that they want you to tear the work apart. Remember that everyone has their own way of doing things, their own style and their own techniques. Instead of saying "You should do (whatever) differently", try "If I was creating a piece like this, I'd try making the (whatever) brighter/stronger/etc". That way you're still respecting the artist's individual style.
* Criticism is not the only route to a 'good' comment. Even if it's not appropriate to comment critically on a piece, you can STILL say something deeper than "Nice work" or "OMG fav". Explain what the piece means to you, what it makes you think of, how it sparks your imagination, what emotional reaction you had to the art, what you think of the various aspects of the piece like colour, form, symbolism etc. If someone has a piece set to 'Critique Discouraged' it doesn't necessarily mean that they don't want to hear ANY of your thoughts on their work - it just means that they are happy with the way it looks (or reads) and have no desire to change it. Also, remember that positive input can be just as valuable as critique - if an artist hears from lots of people that something is GOOD in their work, they they can keep doing that while working on other aspects of their style and technique.
* Don't forget the difference between opinion and fact. It seems obvious, but a worrying number of people seem to forget that just because THEY don't like something, it doesn't mean it's 'bad'. You are allowed to not like something. If we all liked the same things, art (and life) would be painfully dull. So before you go spouting insults through your keyboard into a comment on someone's work, take a moment to remember that you aren't the oracle of all things artistic and have no right whatsoever to tell someone that their work sucks.
* Just because someone doesn't want your critique or doesn't agree with your opinion doesn't mean that they're stuck up or arrogant. Honestly, it doesn't. Sometimes I'm happy for people to give me advice, and sometimes I'd prefer not to get it because I am perfectly happy with a piece just the way it is. Advice from people who are experienced in things that I am working on is always welcome. Rudeness is not. Ever. If you have something useful and helpful to say, THINK CAREFULLY about your words before you hit 'send'. Read your comment again and think "How would I feel about this comment if it was left on my work?". If you KNOW it would upset you, then reword it. The comparative anonymity of the internet is no excuse for being hurtful. And remember...you don't know everything about everything, so while you may have the right to tell someone that you think they should do something differently, they have the right to say "thank, but no thanks...I'm happy with it the way it is".
I certainly wish everyone would take a page out of your book.
Perhaps this should be linked to the people who leave critiques that consist of "omgomgomgthisissobeautifuliloveityou'reawesome and I need to fill the rest of this box, so here! i love it iloveitiloveit" and "i hate it." Everyone could learn to be productive!
Upon re-reading your article I realise I misquoted you in my previous comment. You said If we all liked the same things, art (and life) would be painfully dull which wasn't what I was trying to say at the end of my last one, so apologies !
I recently had some criticism on a piece I'm working on that I feel, could have been phrased better. While parts were helpful, reading what you have said made it clear some parts of the criticism was less opinion and more fact, namey the style I use for hair. The criticism I'm question said my way if drawing hair wasn't realistic, which is fine but my style isn't based in realism; its a cartoony style that I'm still developing and want to call my own. I MAY add more realism to it in the future, but for now I want to develop it my way.
Now I may just be a bitter recipient but I feel you need to respect the artist has a style that may not match your own and you shouldn't try to conform them to it. As a friend and mentor said to me, you should tailor your feedback to offer advice in their style so they can develop it in their direction. I add to this by also saying you should respect what they've drawn and how before you rush in and say fifty different ways why they are wrong and you are right; like you said, if we all drew in the same fashion, there would be no variety to art.
It certainly is a helpful collection of advices on giving constructive advice/critique.
Perhaps this should be linked to the people who leave critiques that consist of "omgomgomgthisissobeautifuliloveityou'reawesome and I need to fill the rest of this box, so here! i love it iloveitiloveit" and "i hate it." Everyone could learn to be productive!
Now I may just be a bitter recipient but I feel you need to respect the artist has a style that may not match your own and you shouldn't try to conform them to it. As a friend and mentor said to me, you should tailor your feedback to offer advice in their style so they can develop it in their direction. I add to this by also saying you should respect what they've drawn and how before you rush in and say fifty different ways why they are wrong and you are right; like you said, if we all drew in the same fashion, there would be no variety to art.
TROLLOL