-Make it very clean, unless it is supposed to be rough like sand or gravel (no random pixels all over the place like the devs used to do).
-Blend highly contrasting colors (this means you would put some purple between red and blue or gray between black and white).
-Use shading sparingly on blocks, you want to make sure they look good when there is a lot of them together.
-Use lots of shading on Items. Jappa likes to make things shiny, and it took him a while to learn how to make blocks tile together. You can see what I mean by looking at old item textures compared to new ones (try looking at the golden apple, diamond sword, saddles, redstone dust, sugar, flint, and other textures to see what I mean).
