Because autofs is implemented in kernel-space, your kernel must have support compiled in. In 2.0.xx it is an experimental option, but appears to be quite stable. In 2.2.xx it is a normal option.
The automount program and its configuration files are also necessary; using the rpms (from RedHat, as part of the install) is a great way to go. The automount program should be started by an rc script under the
/etc/rc.d/init.d directory . The rpm installs this, but you will need to make sure it gets started, either by linking it from your rc?.d directory, using Redhat's control-panel, or on another distribution by getting the thing started anyway you care to. Non-rpm distros will have to do whatever's applicable to their system. And don't look too hard at what the rc script does; if you're reading this howto you probably don't want to know.