USING SYSTEM PREFERENCES:
Select System Preferences from the Apple menu at the top left of your screen.
Click Network from the System Preferences menu.
Choose Wi-Fi from the list of interfaces on the left and click the Advanced button.
Choose the Hardware tab under which you will see the MAC address of your wireless card.
Press Cancel to return to the Network menu. Choose Ethernet from the list of interfaces on the left and click the Advanced button.
Choose the Hardware tab under which you will see the MAC address of your ethernet card.
Launch Terminal from the Applications:Utilities folder.
Type ifconfig into the Terminal window and press the Enter/Return key.
You will be shown data on all your interfaces.
On systems with both an ethernet and wireless connection, en0 will be your ethernet interface and en1 will be your wireless interface. A MAC address will be shown for both en0 and en1 and likely labelled as "ether".
On systems with just a wireless connection, en0 will be your wireless interface. The MAC address for en0 will likely be labelled as "ether".