1) Have a solid design, even tho changes organically come as you build it, having a solid base to work from is always best.
2) Once I have my design drawn up (normally i would have gone thru 3 or 4 variations before i am truly happy with it.). I then think about any special effects I want to install into it.
3) Price of those special effects, such as lights, fog effects, etc.
Once these 3 steps have been met, i go out grab a bunch if not all of the supplies needed and get to work!
What i have chosen to start with is the gem that will be showcased in the shoulders, it started out as a simple oval gem then i wanted more so i turned it into a skull, then that was not enough so i ended up with a crazy looking skull with 4 horns on the head, now that is going to be a truly unique looking gem, here is how it came out post sculpt.