Welcome to Android Forums.
Lots of things can cause seemingly excessive battery drain.
When I first got my LG Optimus V 2 and a half years ago I was in the PlayStore (market back then) every chance I got. This in itself caused seemingly more battery drain than I had expected. Now with the same V I can go 6 hours with screen on, steady helping out here in the forums, on WiFi. Only 3 hours on 3G.
I usually turn everything off. WiFi, Data, Bluetooth, GPS, and Auto Sync (I use Periodic Auto Sync from the PlayStore). I only turn things on when I need them.
If you live to far from a tower then your data will drain the battery quicker trying to find and connect to the tower.
If your screen brightness is to high it will drain the battery.
A bad app can cause battery drain by trying to "call home" to much. Try to figure out which app is the bad one and delete it.
A bad battery.
For more help and support go here:
Samsung Galaxy S3 - Android Forums
Hope this has helped.
AndyOpie150