Chkconfig is a simple utility available on Linux that allows you to register services to start/stop on bootup and shutdown. The following are the basic commands you need to know to get things going:

chkconfig --list (lists all the commands that are registered)
chkconfig --add httpd (add httpd to the chkconfig list)
chkconfig  --level 35 httpd on (enables the httpd daemon to start on runlevels 3 and 5)
chkconfig --level 35 mysqld on (enables the mysqld daemon to start on runlevels 3 and 5)
chkconfig --level 35 memcached on (enables the memcached daemon to start on runlevels 3 and 5)
chkconfig --level 2345 sendmail on (enabled the sendmail daemon to start on runlevels 2, 3, 4 and 5)