Immediately after the equipment and supply check and inventory, the next hour of each shift is spent completely cleaning and sanitizing the unit, inside and out. Doesn't matter to me what condition the previous crew left it in. It's still going to get a complete overhaul from me as soon as I come on shift.
Something that has been quite obvious to me is that, those with a microbiological education happily jump right into the cleaning effort without argument. Those without it want to argue and whine the whole time about how "it's good enough".
A lot of agencies have a policy that the off-going crew is supposed to leave the truck clean. Nonsense. YOU are responsible for the equipment you are using, not someone who isn't even on shift anymore. It has been the policy of any agency that I have managed that the oncoming crew is to perform this function, not the off-going crew. If I find a problem with the unit during shift, it is that crew who is responsible, not some guys who have been home for four hours already.