Hello there, I am tetsuya_shino. I've never written a tutorial (or anything close to one) but I thought I'd try to share what I know. Maybe someone might find it useful. The following is by no means the 'right' or 'only' way, just the way I personally do things.
*The colors, man... the colors...*
Your computer can create and display a dizzying amount of colors.This is great news when you're playing the latest First Person Shooter, but when you're first starting out creating pixel art, more isn't always better.That is why it's a good idea to limit the amount of colors you use.
A palette is a select group of a given number of colors. A palette can be made up of as little as 2 colors or as much 16,777,216 colors. I personally use a palette that has 256 colors. How many (or how few) colors you use depends on a number of factors, but basicly it's a matter of personal taste.
However there will be times where you will be limited to a very small number of colors due to the limitations of a program you are working with. You could also create pixel art with a very limited number of colors, even though the program you are using will all allow much more. Again, it's a matter of personal taste.
A person could make one palette and use those colors for all their pixel work, or they could create an all new palette for each different pixel art they make. Also just because you have a given number of colors in your palette, that has no bearing on how many colors you personally use. Case in point, I use a 256 color palette.
That doesn't mean I use all 256 colors at once, rather I have 256 different colors I could pick from at one time.
Now lets say I wanted to make a pixel object that was made up of 18 colors. I could create a custom palette of with the 18 colors I want to use. However, if I already see those 18 colors on my 256 color palette, why waste time making a second smaller palette? Like a kid in a candy store I can pick colors quickly and easily.
Still, we all aren't clones of each other. What works for me, might not work for you. And vice versa. Keep messing with your palette until you are happy with it. Or if you are forced to use a set palette (as I am), learn to work around it. Good luck.
tetsuya_shino