This is very useful because is saves you from having to buy a remote just for your Pi and also leaves you with an open usb that you would have needed for your wireless keyboard and mouse.
Step 1: Do You Have CEC?
Samsung - Anynet+
Sony - BRAVIA Link or BRAVIA Sync
Sharp - Aquos Link
Hitachi - HDMI-CECAOC - E-link
Pioneer - Kuro Link
Toshiba - Regza Link or CE-Link
LG - SimpLink
Panasonic - VIERA Link or HDAVI Control or EZ-Sync
Philips - EasyLink
If your TV has a button, logo, or menu with one of these names or similar, congratulations you have CEC!
Step 2: Getting Set Up
Get your Raspberry Pi hooked up using HDMI (obviously to use HDMI -CEC you have to use and HDMI cable for video)
Step 3: LG TV
1. Turn on the tv and go to the Raspberry Pi input.
2. Boot up the Pi and wait for it to get to the Raspbmc home screen.
3. Press 'SimpLink' on your tv's remote.
4. Turn it on
The tv and the Pi are now 'paired' and the tv remote will control the basic functions in Raspbmc. Play, pause, directional arrows, ok etc.
Step 4: Panasonic TV
1. Turn on tv to the Pi's input, boot Pi.
2. On the tv, menu - > setup - > Viera link setting - > ON
This tv will even turn on and off when you boot and shutdown Raspbmc.
Step 5: Extra Tips for Home Theater Set Up
2. Use an Ethernet cable and save all your movies on a network drive. Now you don't need a powered hub or hard drives behind your TV.
3. Consider overclocking and using a simpler skin to give a quicker response.