Lesson #2 Form..::Form and Your Vision::.Sprites are not always made with perfect circles or Squares.... many of times they are organic forms forced to be shaped with a grid. Do not forget on any account that you are dealing with a grid. As much as you think it is a free range canvas, it isn't. You are almost always forced with a sharp edge, so don't worry about that.. This part is to indicate that you must take a Grid, and make a desired shape on a forced plane.
A good way to practice spriting, even away from a computer is with graph paper. Draw an organic line on it, then fill in the blocks around that fell on that line, to create a pixelated version of that line, that way you know what to do. That's just for practice though, sometimes you need to improvise.
Form also has to be Proportionate to your desired result... you can't just have it be this oblong shape, and expect it to look like something off the television or your favorite video game. You must be able to create Form without the feeling of that pencil, because believe it or not, your mouse isn't a pencil. And Unlike one, it has it's tricks. In Microsoft paint you are able to use the mouse to create a lone pixel with one motionless click. that is equivalent to filling in a block on graph paper. If you set your mind into that ideal.... you can then start to improve yourself.
Now, in Microsoft Paint, there IS a way to make a grid. That way if you become comfortable with the graph-paper style of creating shapes, you can then adapt it to the Computer.
I will Illustrate how to do so.

Here is the Microsoft Paint Menu.
1. Go to VIEW While you are Zoomed in.
2. Select the Zoom and then Show Grid (NOTE, the Grid only works on X6 and X8 Magnification)

3. Then you have the grid whenever you zoom Into X6 and X8 ^^

I hope this one should help you out and let you use your head more when you sprite in MS paint.