An alternative to purchasing Turtle Beaches.
For this instructable, I will be using a Plantronics GameComm 377 headset, and my Xbox uses a VGA adapter.
Step 1: Materials List
Xbox 360 using either the COMPONENT or VGAcables
Any PC headset withSEPERATE headphone / microphone 1/8 jacks
Things you need to buy;
1/8 Stereo to 3/32 Mono adapter - $5.99
Dual RCA to 1/8 Stereo jack - $5.59
1/8 Stereo coupler - $3.69
20ft. Stereo Headphone extension cable - $12.99
Step 2: Assembly
Click the links for better pictures, because it might not let everyone see them for some reason.
Plug the red/white RCA cables coming off the Xbox into the Dual RCA to 1/8 Adapter
Stick the coupler onto the end of that
Next, plug in your headsets headphone line.
Congrats! You can now hear sound through your headphones, now to make your microphone work!
Plug the headsets Microphone line into the 1/8 to 3/32 mono adapter.
Now, plug that into your controllers headset jack, and you're almost done!
Step 3: Configuring Your Xbox and Game Audio Levels
Turn on your Xbox, and bring up the Guide (xbox button on controller).
Go to the Settings tab, and select Preferences.
Make sure Voice volume is set to 10, and check Play through speakers.
That's it! You're done!
Enjoy your headset, and kicking everyone's ass with it.
Step 4: Troubleshooting
Voice chat is very quite / can't hear it over the game noise.
If your game has an actual in-game volume adjustment, turn that down until voice chat becomes audible.
(MW2 has the volume slider under Options at the pause screen in multiplay)
Now that I've adjusted my game volume to be able to hear voice chat, my game volume is too quiet.
I had this problem, my solution was to buy an inline headphone amplifier. You can find them online for between $10 and $20, This is the one I use, works beautifully.