For example, if you do not want wlan0 to be started at boot time,
just move ifcfg-wlan0 file from /etc/sysconfig/network-scripts/ directory
to any other directory.
I am telling not to remove the file, because you can start
wlan0 interface after copying the file back to /etc/sysconfig/network-scripts/
whenever you want. And give command
# service network restart