If the aircraft I'm flying has a reliable amp meter I use this to check that my pitot heat is working, if not I check if its warm.
The aircraft I fly at the moment has an amp meter that indicates all over the place, so I have to turn everything on to see any difference (still indicating all over the place but in a different pattern
)
Checking landing light and pitot heat with amp meter saves a bit of battery during your walk around (good at this time of the year).