The last time I looked at the AAMD Salary Survey, they had very brief job
descriptions for each position in order to standardize the data (i.e.,
Curator, Asst. Curator, Assoc. Curator, etc.) across museums of various
sizes.  One museum's Assoc. Curator in title might be another's Asst.
Curator.  You might try checking with the AAMD, but job descriptions in
other types of museums other than art may vary.

We also keep back issues of AVISO to use when writing position descriptions,
assigning titles, etc.

Finally, if you are looking for job descriptions for specific titles, you
might poll this list!

Julia Muney Moore
Director of Exhibitions and Artist Services (I think--I've been on vacation
for so long I forget  :)   )
Indianapolis Art Center