Now, you should decide on a window manager. The X Window System is simply the environment which allows graphics to be displayed on your system's hardware; the window manager is responsible for how X looks and how it interacts with you and your applications.
The Red Hat distribution of Linux contains several window managers, including fvwm, olvm, twm, AfterStep, and others. The default one that you will probably see when starting up X for the first time is fvwm95, a Win95-like environment.
Personally, I find the usual offerings differ from my own tastes, and I recommend using either GNOME or KDE (or both!), whose installation are covered in the next two sections.