I was told never to use it after training (as you sweat and have less water in your body).
Anyway., Law of Common Sense tells me to use it:
Every morning, after peeing and taking a dump
Before any breakfast or liquid intake
about the same time
naked
That is, in that way you should see, at least, a weekly trend (don't take any particluar day reading too seriuosly) and never measure twice in a day (doesn't mean shit).
This is what I do.
I alsd learned yesterday from the Scientist guy, that since current travels the shortest path, it goes through your butt, where there is always a higher %age of fat.
Pintoca