I've seen plenty of guides about how to make sprites in MS Paint and the like, and that's all dandy and swell, but there's an easier way (well, to some people). For this guide, you'll need Photoshop CS3, some sort of drawing tablet that has pen pressure capabilities, a decent amount of drawing skill, and a general idea of shading. Not too hard, right?
First, start with your canvas. It should be 512x384. That's right... double the size of a standard DS screen.
This is how I do my sprites: I draw the basic guidelines first, to get an idea of the pose. For these, I use a size 9 brush (size depending on pen pressure) and I try to use a lighter color (grey-ish, so it doesn't get mangled with the clean outlines.) Then, I draw the clean outlines on a different layer so that I can color later. Use a size 2 or 3 brush where the size is fixed - not altered by pen pressure. After you're done with the clean outlines, you'll be able to start coloring on a separate layer. For Phoenix Wright sprites, 16 colors are used. Apollo Justice sprites use 32. Try to keep your colors within that limit. After the coloring and shading are done, resize the canvas so that it's 256x192 (bicubic is the best setting.) Make sure to also delete the layer with the rough sketch. This is the tough part: on the bar at the top of the screen, you'll see a button labeled "image." Click that, and a drop down menu will appear. Hover over "Mode" then select "indexed color." You'll be asked if you want to merge layers. Say yes. After that, a window will appear. There will be a selection reel entitled "palette." From that, select "Local (selective)", set the amount of colors to 17, and then make sure that the "transparency" box is checked.
The end result:
It's not the best sprite I've made (and it's not the most original...) but it works!

Thanks for creating a guide, Virt! It looks pretty cool, but unfortunately, there's a couple of issues I have to point out. The first is administrative wise that you posted in the Art Guide forum without your guide being run through myself first. Please read the Submissions thread next time, but this is a no biggie.

The second issue is more major. I'm sorry to say that I'm going to have to ask you to rewrite this guide. At the moment, the core of making sprites is barely ten lines long and as a result, it's not quite clear about what you have to do. Have a look at some other spriting guides -- Singidava's, for example -- and look at how it presents itself. Images are a must for something along these lines,

"For this guide, you'll need Photoshop CS3, some sort of drawing tablet that has pen pressure capabilities, a decent amount of drawing skill, and a general idea of shading."

This seems a tiny bit of a turn off to most users... you could rephrase it to be more friendly. Not everyone on AAO uses a drawing tablet -- most users are content with a trusty mouse, or even a touchpad. "General idea of shading" could be expanded upon, to give potential artists who don't know their light sources a couple of links to tutorials and such.

When writing a guide, place yourself in the feet of your intended target audience. Imagine that you haven't had your experiences, and think of how they'll read and interpret the guide. Good luck!

I saw the big block of text and was immediately turned off... Separate your ideas or steps into different paragraphs.

Also, I think that making the canvas 4x the DS size, using a size 5 brush, and using colored outlines is better...

I must agree with Tap about this guide. Instead of being a full-tutorial it feels more like tips. Well, most of the tips are good but there is some things I must disagree with you:

First off is naming of the guide. I realize that you didn't do this intentionally but "actually" has a bit condescending tone to it or at least that's how it seems to me. In order to make the guide more user-friendly I'd advise you to use different wording. Another thing is that the naming is a bit misleading since that is not the way Capcom actually creates their sprites. Instead of going straight to DS size they first create their emotes much larger, the kind you can see in Ace Attorney HD. After drawing the picture the characters are shrunk to the DS size and finally they limit the palette. I used the style you describe in I created some of Andrew Webster -sprites. However, later on I found that the way I currently make them (check out my tutorial) got me much beter results.

Thanks for the feedback. Sorry, this is my first guide and I really don't know the run of the forums yet. I don't think I really need to rewrite it though, since I just found another guide that's almost exactly what I had to say, but better. I guess I'll just lock this thread.