I have a couple of seperate books reserved for 
just one series, and one for assorted stuff.  
Stuff generally goes in in the order I get it, 
with the sketch on the bottom page as you open 
the book, so that you can see the cel and sketch 
together.  This means I have to occationally move 
things around to accomodate the sketchless or 
stuck-to-sketch cels, since I try not to leave 
open pages.  If the image is really small, I will 
put the cel and the sketch togther, just offset 
slightly so both can been seen (seperated by a 
plastic bag, of course).  Sequences are grouped 
together, in order.

For what it's worth!