Sprite ripping, as you should know if you read the glossary (assuming it's up), is the process of taking sprites from a video game using emulators and ROMs.
Just in case you don't know, emulators are programs that run ROMs of video games. ROMs are essentially all the files from a game cartridge placed into a single file, with any number of possible extensions, just as SMC, NES, ROM, v64, etc etc etc. You can get emulators from a lot of places on the net, and ROMs from emulation sites as well, but be warned; emulation is illegal. The counter-argument is that a lot of these games are so old that it's impossible to buy them anywhere, so only emulation of more recent systems is checked up on. For more details check the disclaimer on your local ROMs site.
I'll assume that you have the ROM you want, but I'll only list procedures for the emulators I use. They're pretty much the same for other emulators, so it really doesn't matter, but it will when I do a tutorial on sound ripping in the future.
My SNES emulator is ZSNESW (ZSKnight's Super Nintendo Entertainment System for Windows), just so you know, and it's a mighty fine one at that. The process is the same for ZSNES DOS as well, in case you're using that.
First, load the ROM you want to rip the sprite from. Find the sprite you want to use, and simply press the snapshot key ('Delete' by default), and you've got the sprite. This is the easiest method but it's a lot harder to rip sprites like this as you manually have to remove backgrounds.
It is possible with some emulators to remove layers from the window, such as the foreground layer, background layer, and sprite layer. If you remove all layers except for the sprite itself, you can rip it much, much easier.
If you want to rip a sequence of sprites, then right before the sprite comes up on the screen, press the F1 key and select "Increment frame" until the sprite is on-screen. Then, select "Snapshot/Increment frame" until you have all the sprites you wanted. You can also use this if the single sprite you want only appears for a very short period of time.
If you check the folder that contains your ROMs, you'll find some BMP files labelled "Image1", "Image2", and so on. These are the snapshots you have taken, and you can then rip the sprites from here if you so wish by simply copying and pasting them to wherever you want them to be. If you removed the layers around the sprite you can usually just use a fill tool to eliminate the background, which will probably just be a single solid color.
That's pretty much it; you've got your sprite now to use in your sprite comic or add to a sprite sheet or whatever. If you use the Printscreen key, though, be careful, as the images tend to be stretched compared to the image a snapshot produces.
Game Boy Advance games are very new and as such GBA emulation is illegal. This makes it very hard to find ROMs but it's still possible if you know where to go. Knowing a word or two of german or spanish may help...
The same process applies to Game Boy and Game Boy Color games, since GBA emulators almost always run GB and GBC games as well. My emulator is Visual Boy Advance, which does not have a snapshot feature but does allow you to change the size of the window that the ROM runs in, so you can use the Printscreen key.
I use this process to grab sprites for use in DMBN. Make sure the window size is set to "1x", and find the sprite you want, removing layers with Ctrl+1 to Ctrl+5, depending on what layer the sprite is in. Use Ctrl+N to advance the game one frame at a time if you so wish, then hit the Printscreen key to snap the sprite. Paste it into an image editor, and repeat if you want a series of sprites.
GBA sprites tend to be a lot more complex than SNES ones; it took me at least a week to figure out the best way to make the sprites for DMBN. That said, even in newer games you can usually find that the sprite is made up of only a few different colors, six or seven at most, so you can use a color substitutor to edit the sprite if you so wish.