I made a small demo program a while ago that shows how I do it. It also shows how I handle multiple screen update methods in one program. It's based on the Allegro demo game, but hopefully it will be easier to understand.

You can get it from

http://www.science.uva.nl/~eglebbk/download/upddemo.zip

Hope it helps...

Evert

The concept behind dirty rectangle code ...
The dirty rectangle method of rendering is based upon the concept that one need only redraw the part of the screen that changes from frame to frame. I will focus on the case described below:
I have a relatively static scene, and I want to put moving characters on it.
(1) For each character, have a buffer bitmap the same size.
(2) Copy the rectangle that the character will be blitted to into the buffer (b4 drawing the character, of course).
(3) Masked blit, or whatever, the character to that rectangle.
(4) When the character needs to change position, copy the buffer to where the character was ... erasing the character.
(5) Go to step (2).
(edited: sp and such)
[ September 08, 2001: Message edited by: Zaphos ]

Umm ... have buffers for each sprite (of corresponding sizes) and buffer the static scene for every sprite before drawing the sprites to the screen ... or just remember the order you drew the sprites and buffer as you go ... it isn't much different. Just follow the same process a bunch of times.
The original instructions were written for multiple sprites actually.
here, errata step five to:
(5) change char to the next character to draw, then goto (2).

Does the layer in front of the character change? If not, and if you are using double buffer redraws, try this:
Use masked blits, and have three standard bitmaps of screen size. One will hold the backbuffer, as normal. The other will hold the background, stuff that goes behind mr main character, and the other other will hold the foreground, which will all go infront of the character. To initially draw the screen, blit the background, then the character, then the foreground. Character may be replace with characters. Always masked blit the character and the foreground, so that everything is see through and you don't cover the screen up. Always std blit the background, so that you erase what ever was beneath it.
When you want to move a character, copy a rectangle of the size and position of the character from the background bmp to the back buffer (unmasked blit, this is your character erase), then blit the foreground. Then blit, to the new location of the character, the background, then character, then foreground, always only blitting enough rectangle to cover up where the character is to go. This method takes more ram to begin with, but no longer requires a buffer for each moving sprite ... so it all depends. If this explanation is too confusing, I wouldn't be surprised if it is, just demand of me a code sample, and I'll be happy to oblodge (darn, I could never spell that word) you.

Well, I've been working with the code a bit..
thankfully, I got it up to 40fps..
However, I need to always blit the foreground I think.. when I use the same system for the foreground as I do with the background, it doesn't blit the background.........doesn't even make sense, really..
I'm going to work with it some more. I'd post some code, but I don't have it with me (at school).. Thanks for your help guys