Here's my secret recipe for making a sculpture. The first step is to agonize over a design inside a 3d application on the computer; I use Sketch-Up at this point. Back in the dark days on Windows, I used Rhino for my design workhorse. It is a much more powerful, and therefore more complicated, program. There are programs of comparable power on the Mac (formZ pops to mind), but I've fallen in love with the idea of simplicity, and Sketch-Up is elegant and spare in it's design, but plenty capable for my needs.
I'll use my sculpture "Pharaoh's Dream" to demonstrate. My design goal on this thing was to somehow convey the idea of the impermanence of the ego and the folly of erecting monuments to it. The Egyptian Pharaohs who sought to glorify themselves by ordering the creation of the great pyramids really only succeeded in underscoring their own mortality. What comes to mind when you think of Ancient Egypt? For me, it is the pyramid, stripped of any creator's name or identity. So I chose to symbolize this by having only pyramids spiraling up to the heavens out of the great archetypal base pyramid, rather than any trace of the pharaoh's transcendent ego. Dust to dust, indeed.