I actually just made my first boot animation last night. So, I'll tell you what I've learned, which might not be specifically "right" answers, but should get you started.
My bootanimation consisted of two parts. Seperated into two seperate folders, "part0" and "part1". The first part contained a set of images in PNG format, sized for our phones (320 x 480), that I only wanted to play once. The second part contained a set of images to loop after the first part played.
So, you make those up how you like, just using Photoshop or whatever your preference is. When saving them, you can name them whatever you like, just make sure to have them numbered, and no spaces. So, something like "my_boot_000.png, my_boot_001.png"... etc...
Next, you need a text file named 'desc.txt'. It contains the following:
Code:
320 480 30
p 1 0 part0
p 0 0 part1
The 320 is the width of the screen. The 480 is the height. 30 is the "speed" of the animation, you can adjust this to your liking.
Picking apart the next line, p 1 0 part0
p -- the p is just there, not sure what it stands for.
1 -- The 1 tells it how many times to play.
0 -- The 0 is a delay in milliseconds.
part0 -- part0 tells it which folder to play.
So, the next line is p 0 0 part1. This is basically the same, although the 0 instead of the 1 causes it to loop until the phone has booted, which is what I wanted.
After you get all that done, you're going to make a zip file called 'bootanimation.zip'. It should look like this:
bootanimation.zip
part0
part1
desc.txt
Copy it into the appropriate place in your ROM. I was running AOKP, so it was /system/media/bootanimation.zip
You can download my animation and pick it apart if you'd like, just to look at a "finalized" one.
http://dl.dropbox.com/u/72059024/bootanimation.zip