I'm gonna make a "guide to successful posting" designated for the "graphic" sections and I hope (if its good enough) that it'll be stickied.
1. When someone posts a sprite(sheet), title screen, tileset or any form of artwork, instead of posting "OMGZORZX DATS DAKOOLEDST THIngG EVAR!!11one" try to make your post more beneficial to the person who is displaying their art. Say WHY you do or don't like something, and give ways to improve the peice.
2. If something is really bad, don't come off as a jerk, address the artist with maturity and kindness. Tell them how they can improve in a POLITE manner.
3. It's okay to compliment the peice, just be sure to say what you like about it or why you like it.