Imagination comes first, and is the most important factor.
Nothing beats a deep, primal, good idea.
It's not the equipment that does the work, it's the people. It's experience, not chips and wires, that makes the magic. Thorough prior planning is absolutely crucial to success. In any highly technical shoot, you just can't wing it without putting a torpedo into your budget. We'd first like to draw a distinction among several different Ultimatte styles or situations.