Devices
What type and size devices need to be housed in the units, e.g. Television, Sky Decoder, Stereo, Surround Sound, Gaming Consoles etc.
Style
Is there a design style that you really like or look you are trying to achieve?
Storage Requirements
Do you have any particular storage requirements, e.g. DVD’s, CD’s etc.
Height of Unit
What other elements will be positioned near the unit? e.g. Wall Mounted Television, Windows, Fireplace etc.