What is the proper method to remove old kernels from a Red Hat Enterprise Linux system?

Issue

• How can I remove old kernel packages from a Red Hat Enterprise Linux system?
• Two kernel packages are appearing in my system, how to remove the older kernel package?
• My /boot directory is getting full, how do I remove old kernels?

# df
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                      14804452   7006156   7046272  50% /
/dev/sda1               101086    101086         0 100% /boot
none                    127332         0    127332   0% /dev/shm