If you have an older Electronics glass case setup, you are pretty much going to have your hands full during the holidays/ taking care of guests. If you have the newer model, just engage the guest and ask what they are looking for.
Half the time the guests don't know what they want or what they are looking for.
All your immediate needed info are on the placards.
But you should know your
ESP
TV resolutions 720/1080/-i/-p
Video cables
Audio cables
Computer cables
Pros/Cons Lithium & alkaline battery cameras
Camera resolution
Memory card formats
Computer storage -byte sizes (GB/TB)
Reliability/Quality of your cameras, TVs, electronics
Really just walk your Electronics area, and know where things are. Know where your MUST HAVE games/movies/electronic items are at.
For attachments, engage the guest find out what they have always push the extra things they might need, the better cable, the mount, controllers, games, ESP...
Read up on electronic items on g4TV, cnet, makeuseof, tekzilla