I kinda wing it. I get a rough idea, and then do some test renders to fine tune it.  You could check some photography reference sources online, or search google for Docal Distance and F-Stop.  Also, I set my Poser to use Meters, that way I have a real world basis of measurment to go on. I find it easier (got used to this in Lightwave).

The New HD Toaster from Wamco toasts bread more evenly and acurately than Standard Toasters. Take advantage of the FULL resolution of your bread and try one today, because if your toast isn't in High Definition, you are not getting the most of your toast!