Go to the Xbox Dashboard, and go to system settings select Memory and hard drive and press Y.
Clearing the cache is a simple process, and can be useful if the system seems sluggish, unresponsive, or you just need to get rid of a game update (for whatever reason).
All downloaded game updates will be removed. So if you have downloaded an auto-update for a game, in order to play it on Xbox Live you will need to re-download it.
User game saves, profiles, demos, videos, etc. are not deleted during the process. hope this helps :)