How do you do a black background on small things?  I tried this using black paper, but, it came out bright.  Just curious what everybody here uses.  

if using photoshop, use the select tool and select the background.  tweak the accuracy adjustment till it collect enough of the varying background.  Then use the paint bucket to fill the selection.

Theres prolly a better way, but thats what comes to mind.

Distance.  The ratio of:

A:  Distance from light source to subject
B:  Distance from subject to background

must be small.  (i.e., there's 2x-3x more distance from subject to backdrop than from light source to subject.)  Assuming your light source falls off "normally" (i.e., it isn't a focused beam), then getting the background far away makes it fall of quickly.  (Inverse square and all.)

Yep, you need a good amount of distance between your object and background. It also helps to be able to control your light.

This is a setup I've been wanting to try out once I stop buying firearm related items and buy a proper background.
http://www.diyphotography.net/light-up-the-floor-a-floor-lit-table-top-studio-project