Folks have mentioned several ways to pick up information >from a worn stone.
Several considered are incorrect and not allowed in most cemeteries. Both
chalking and rubbing can cause great harm as will shaving cream and flour.
Please see the link below for safe methods and effective methods.

http://www.ncgenweb.us/newhanover/cem1.html

also

http://www.ctgravestones.com/Conservation/inscriptions.htm .

The stones belong to posterity lets not damage them.

Bob Roudman
San Rafael, CA