You'll need pee :)
may as well get some poo while you're at it. Fresher the better.
How does one get pee!
Usually I wait with a takeaway container (large dog people use frypans or saucepans). Anyway, take them outside or for a walk, you stalk them and when they get into the pee position, swoop in with your catcher. :)
Bahaha...okay :)