I feel like critiques are important not just for the artist receiving them but to the person giving them. Critiquing some one's art forces you to think about your own, to notice the little details that set a piece apart. Understanding what you do and don't like and most importantly why is how you get better!
But giving a good crit is hard! You want to be nice (hopefully) but you also need to point out some thing that is wrong or at least not as good as it could be to some one who put a part of their soul out on, in this case, the internet. A thing that in its' self can be painful.
I've found the best way for me to give a crit is to follow a