Here is a complete list of RefTeX’s configuration
variables. All variables have customize support, so if you are
not familiar with Emacs Lisp (and even if you are) you might find
it more comfortable to use customize to look at and
change these variables. M-x reftex-customize will get
you there.
In case you don’t use the customize
interface, here’s a caveat: Changing (mostly
parsing-related) options might require a call to
reftex-compile-variables in order to become
effective.