There is lots of information on X Window to be found, on your
computer right now, on the Internet, and in some excellent books
available at your favorite bookseller. Give some of the following
resources a try, they have been extremely helpful to the author, and
can be extremely helpful to you, too.
The man pages for X, xterm, XFree86,
and
for any other clients you find yourself using often, are very useful
and
quite information-packed, and highly recommended. As the oft-repeated
saying goes, RTFM.
There is a Remote X Apps MINI-HOWTO that is very helpful
in
figuring out how to run local and remote clients with X.