Hey Wozzah,
Looking into the valve . . .
Morgan
Disposable or refillable? If it's disposable, remove the regulator and if the pin is sat well below the top of the threads it's empty. The pin will also probably rattle if you shake the cylinder.
If it's refillable then remove the regulator, carefully open the cylinder valve slightly (pointing the outlet away from you of course) and see if gas comes out.