I simply use:

<modelname>_<date><version>

e.g,
brutus_20060927a
(date in reverse and UK standard as I do programming - at least its not in unix timestamp)

and then when finishing working, save it to that version and also save to the next (e.g, brutus_20060927b) so that when I next open maya I'll have a copy of version a to work on and more importantly two identical versions in case either gets corrupt.

Si