Important things to know before you start the tutorials

First off...
I'm still in the middle of trying to learn these things myself. I am NOT a professional. So my word is not absolute. In fact, you should read as many tutorials on the same subjects as possible so that you can find the most comfortable and efficient way to do the same task. I'm simply presenting what I have learned (both through reading some tutorials and through figuring some things out on my own).

Consider your hardware
I'm running on an Athlon 3000xp with 1.5 gigs of memory and an nVidia GeForce 7600. I can handle a 2000-3000 pixel wide image. However, not everyone's computer is well equipped. If you have limited speed, memory, or graphics capabilities, you may be required to work at a lower bit depth and/or resolution.

The tablet I had was not used in any of these tutorials. I did this on purpose to show that anything and everything I am doing can be done with a mouse. If you have a tablet and you would like to use it, go right ahead. More power to you.

Choose your software wisely
There are plenty of image editing programs out there. Some are very expensive. Some are cheep as dirt. They will definitely have different features, but in the end, the overall result of your image depends not on the software, but how much time you invest in the image. Idealy, you should look for a program that uses layers, has selection tools (lasso, polygonal select, rectangle select, elliptical select), has basic painting tools (paint brush, pencil, airbrush, bucketfill), and can save is the .PSD format (the default format for Photoshop), and can export as some, but not all, of the following formats: Bitmap (.bmp), Portable Network Graphics (.png), Joint Photographic Experts Group (.jpg or .jpeg), Targa (.tga), or Graphics Interchange Format (.gif).

(Note that some programs, while supporting .jpg and .png, will open but won't allow you to save .gif files due to some mumbo-jumbo about liscensing agreements...)

I'm going to assume that you know what the tools do. In some instances, I will explain how to go about using a tool, but I'm not doing it for every single one. It is also a good idea to either memorize the current shortcut buttons on your keyboard or assign new ones to tools in your program that you use the most.

Here's a small, broken down list of some programs I've experienced. This assumes you are looking for image editing programs that use raster layers only, not vector layers:

Program: Price: Platforms What it's like:
Adobe Photoshop $649.00 Windows, Mac Photoshop is THE industry standard when it comes to digital imaging of any kind. It is top rate, very stable, and has a lot of features. It even allows you to customize brushes for different effects and looks.
Corel Painter $394.00 Windows, Mac Fast becoming a popular product in the industry, Painter is a top notch program that allows you to produce realistic (VERY realistic) paint-like digital work. It's very easy to produce an image that looks like it was painted with watercolor or oil paint in Painter. The trial version of Painter I used a long time ago was pretty neat, but I found the interface a little hard to work with. It might takes some time to get used to.
Portal Graphic's Open Canvas Appr. $60 ~ $70 (depends on the version you get) Windows A Japanese program very similar to Painter, but a little cheaper. There are no boxed versions to my knowledge (it's download only). It was surprisingly good to use in my opinion, but just like Painter, doesn't have the easiest to use interface.
GIMP
(GNU Image Manipulation Program)
Free Windows, Mac, Linux A free image editing program. GIMP is a good open source image manipulater. It is maintained and enhanced by people who use it and there are some plug-ins that you can download. One annoyance of GIMP is the fact that the windows are free floating on the desktop, so it becomes very cluttered very quickly.


Pixels
All images you see on your computer are made of pixels (short for "picture elements"). A pixel is a small, slightly rectangular box that is full of color. How well your screen displays pixels depends on your graphics card and the screen resolution of your monitor.

The color of a pixel is determined by how much red, green, and blue the pixel contains. These are colors used in light. Each color ranges in a value from 0 to 255, making 256 possible values for each color. When all colors are at a value of 0, the resulting color is black. When all colors are at a value of 255, the resulting color is white.

It is HIGHLY RECOMMENDED that if you want very good image quality, you run your computer at a color depth of at LEAST 24 bits. This gives you the greatest amount of color (over 16.7 million).

(NOTE: Red, green, and blue are the primary colors used in LIGHT! Red, blue, and yellow are the primary colors used in PIGMENTS!)