In order to find the MAC addresses available on current cards run:

grep -H . /sys/class/net/*/address

Edit:

/etc/sysconfig/network-scripts/ifcfg-eth(x)

For a DHCP, on-at-boot card named eth0:

DEVICE=eth0
BOOTPROTO=dhcp
HWADDR=00:E0:4D:0C:6B:32
ONBOOT=yes

Modify the Device name to modify the name you use in scripts and in bash.