I would consider looking into slightly more capable software, like Paint.net or GraphicsGale (both free downloads). For example, here's a GraphicsGale tutorial (not necessarily the best one): http://www.youtube.com/watch?v=mtuxBMRrfVY
As for tricks, I'm not sure there really are any, Paint's pretty simple. You can hold Shift to draw straight lines with the pencil tool, if that's what you're referring to. The color picker and eraser don't have shortcuts as far as I know. Here's some more info about paint: http://www.drububu.com/tutorial/mspaint.html
Here are some generic pixel/art tutorials that you should look at, too:
And of course my more generic article about game art in general:
Just remember to practice, practice, practice. That's 99.9% of becoming a better artist.