That's what little parts boxes with lots of separate compartments are for.[1] That's one of my projects.

[1] http://brassgoggles.co.uk/forum/index.php/topic,43672.25.htm...

Use a big piece of cardboard. Screw screws into it in the same order they came out, and draw an outline of the part they came out of. Tape down small pieces that aren't screws. Label everything with Sharpie. It slows you down enough to prevent a lot of mistakes.

I had once had to take apart an optical camera.

The approach which worked for me was:

a) Unscrew a few parts b) Screw them back c) Unscrew a few parts and some more d) Screw everything back in that same order ) .. repeat until done

Finally, it all ended well