Most of the icons I make, I don't draw, I just fond some simple graphics, cut out the background, fix the edges, shrink to 32x32 and see if it's still recognizable. If it is, then I see of 16x16 is still halfway recognizable too. If that isn't, I may pencil in the 16x16 by hand. Making something on a 16x16 pallet isn't hard!

The beauty of icons, is that each size is a completely different picture, and thus, can be a completely different thing. An example is the icon for our flagship produxt. At 32x32, it's our product logo, a colorized, stylish image. At 16x16, that logo becomes totally unrecognizable, so we just used a simple white box with the company's initials "DS" in it.