My rear projection Sony TV, is about 9 years old, and the rear of the
screen needs to be cleaned. I have heard, if not cleaned property, you
can damage the screen.  My question is : What is the best way to clean
the rear side of a rear projection screen?

Hello Clicker5,

You are certainly on the right track. In reviewing on line material -
the caution that is repeated over and over again is to not rub the
surface. That will damage the material.

After that, there are a number of different methods recommended by
vendors. If you can find the user's guide from Sony, that would have a
recommendation specific to your TV. Suggestions from other vendors
include:

 - use a soft cloth with water or mild soap and water. Dry with
another soft cloth. (look about 1/2 of the way down this file) These
also suggest mineral oil for minor repairs - but I can't tell if the
material is similar to what Sony uses.
  http://www.noxtat.com/tecnical_info.htm
  http://www.dalite.cz/polacoat2.htm
 - a vendor selling a kit for cleaning rear projection displays (low
residue cleaning fluid and cloth)
  http://www.tritronicsinc.com/proclean.html
 - remove dust with a cloth or vacuum with a soft brush. Remove stains
with soap and distilled water.
http://www.draperinc.com/images/RearScreen/instructions/DiamondScreen_inst00.pdf

If you are still uncertain, you can either
 - check with a local TV repair facility to see if they will clean the
screen for a reasonable fee.
 - do a small portion on the edge of the screen, (e.g., a part covered
by molding) to make sure the surface can be cleaned and will not be
damaged.
Good luck!

  --Maniac

Great answer - more information than I expected. Outstanding service.