[konidias]

1. practice

2. practice

3. practice

That's how you get better. Of course practice involves actually looking at other artwork and learning how to draw... and then drawing. a lot. Every little technique you learn makes you a little bit better. Oh and if you really want to make great artwork, your best bet is to always start with rough sketches. You need to learn the art of the rough sketch. Once you can rough sketch something out... it becomes easier and easier to "flesh" it out into something amazing.

If you're speaking mainly of pixelation.. then you need to be able to visualize the finished image in your head as best as you possibly can and then use it for reference. Then after you finish, you should go back over it and fix the coloring, shading, outline, etc... until it's just like you wanted.