> A lot of software people like to jump in and I see them portray the planning people as trying to figure everything out first.

My approach, especially for a project with a lot of unknowns, is usually to jump in right away and try to build a prototype. Then iterate a few times. If it's a small enough thing, a few iterations is enough to have a good result.

If it's something bigger, this is the point where it's worth doing some planning, as many of the problems have already been surfaced, and the problem is much better understood.