now i did this in photoshop 7, but i'm sure any version would do-- and i'm sure you could do the same thing in paint shop pro (but i dont use psp so i wouldnt know)
anyway-- onto the tutorial!
i'll be leaving simpler notes along for those who dont want to read all of my sensless babble ^^

as with almost any good picture you're gonna need a sketch to start with sweatdrop otherwise

ink what you want to keep-- make your lines thick enough for the wand tool to select them when you use it--

basically-- crop off what you dont want... i highly reccommend leaving alittle on the sides-- as it becomes a bit of a pain when you're trying to color something and the layers toolbar, or history ( or whatever you use) is in the way

adjust the brightness and the contrast-- i also suggest playing with the levels too (ctrl+l)

remember when i said it's good to make thick enough lines to grab with the wand tool? well it's time to do that... select the wand tool (w) and select a line, then zoom in and make sure you get all of the parts of the picture that you've inked (or that you want)

now select the lasso tool or the marquee tool (l or m) and right click anywhere on the picture and select the fill option, and fill the area with the foreground (or backgrond...depending on what setting you have it on) color. but be sure to do it on a new layer above the original image!

now be sure to make a different layer for every different part of the picture that you're coloring and fill them in appropriately
(there's 2 methods for doing it, either take your time and just fill it in nice and pretty so you dont have any erasing to do... or you can do like i did and just go nuts and use the lasso (i prefer the polygon lasso) to erase the unwanted parts of the coloring...

heh...i seem to have gotten a little ahead of myself on this one <<; so just go up a bit or reffer yourself to the picture above...

now that you're image is nice and colored (whichever method you chose...)

now just use the polygon lasso to make some zig-zag's on the bangs (all of my characters have unusual hair so to get a normal highlight on hair, you'll have to reffer to another tutorial or hold it out so i can come up with a better tutoria ^^ wink
anyway~ fill it as you did the lines in the earlier stages (with transparency locked) with a much lighter color than the original (NOT WHITE)

once you have your zig-zag things in place and colored correctly you may commence in using the smudge (rub...whatever you call it) tool to rub it all together-- now the secret to the smudge tool is strength and size-- i reccommend using a 20-25% strength, and a 20-24 size when smudging...
(note: this should have been done on the same layer as whatever you're adding highlights to...)

(now i did the same to the back of good ol' mael's hair...you dont need to do this, but if you want to go for it)
start adding shading to the spots where you think shading belongs on your picture
with the assistance of the polygon lasso tool...

but i also reccommend doing this in different thicknesses (example, use the eyedropper tool ( i ) to copy your base skin color, and darken it alittle, fill all of your shading in, then darken the color again! and go over it again, but closer to the areas where the light is being blocked (if that makes any sense) and fill it again, do this as many times as you feel nesissary)
and you should have something like the picture above-- (results may vary)
finally smudge them as you did the highlights in the hair

you should get something like this...
now i had a final product but my computer froze up when i got to the final step-- needless to say-- i was very angry... but that pretty much concludes my tutorial.... i hope you've enjoyed-- or at least learned something.
any questions, comments, or concerns-- please pm me or just post it on here @_@ i'll try to get to you as soon as possible...