Kicking the tires

I do, but not on a car.
I don't know why that term got started on car lots, because you can tell just by looking at a car if the tires are low.

On a big truck with two tires on each side of the axle, you can't just tell by looking if one tire is low.
So, lacking anything else- you kick it to see how solid each one is.
Actually, I've always had better results with a hammer because I can feel the different way it bounces if one of the duals is lower than the other one.


Another useless thing I've seen is that blowing non-existent smoke from the muzzle.
I saw River do it last night on Dr. Who.

The original reason for blowing DOWN the barrel was to help burn off residual embers in the firing chamber before you poured more black powder down the barrel. Otherwise it would flare-up and burn you.
That's why you see artillerymen swabbing the cannon barrel before shoving powder down again.
That's also why you don't pour black powder from the flask directly down the barrel, because then you have your hand around a black powder grenade.

Of course that need went away when they came out with the metal cartridge, but I guess old habits die hard and we see old movies carrying it on.