Are you after help with timing or with character movement speeds?
If timing, see this tutorial about timing in Java games:http://grexengine.com/sections/externalgames/articles/Kevin%20Glass-Space%20Invaders%20101-2.html
Remember also that Java 5 now has a System.nanoTime() method.
Does anyone know if this new method is accurate on Windows?
(i.e. updated more than once every 10ms and doesn't drift horrendously?)
If you're asking about character movement, I can only say "what I would
do", which is to define the movement of characters relative to each other and then find some way to translate these relative values into the right units.
If you're wondering about what units to use, I would guess people use pixels for a 2D sprite-based game, or the units of the "game world" if you're doing 3D, but I don't really know.