as fresh as possible but you can put in a ziplock baggie with a wet paper towel and put it in the fridge. I have kept it in there from the morning til the late afternoon when I had my fecal done at the vet. you don't want it to dry out.
as fresh as possible
my vet doesnt suggest anything more than 4 hours old. But if kept moist and in fridge, overnight can be acceptable.
Happily for me, I dont need an appointment to drop off a fecal - so anytime I see a cham leaving me a present, I can immediately take it in (unless its Sunday, when the lab techs arent working)