selecting a window manager (for newbies)

[Rich Rudnick <nickrud citlink net>]

my first post to any linux-related site, so please be kind:

How do I change the window manager that gnome uses?  I've been using
enlightenment 1.5.5, (came with RH6.1),  upgraded to 1.6.3, but would
like to check out sawmill.  I've gotten the RPMs from sourceforge.net,
but before installing I'd like to understand how to configure X to use
*any* window manager.  I've looked at the man pages, FAQ, info, etc.,
but unless I'm missing something obvious I cannot figure it out!  Would
someone please point me in the right direction?  My thanks in advance.