How do YOU develop software?

[demosthenes2k8]

This is copy-paste-modified from a chat log I had with a teammate about the exact same process:

I normally start by defining the problem - for robot code, I make a list of all the different sensors, motors, etc. and group them according to functionality - the four drive motors would be one section of the code, for instance. Then I would go create the "essentials" - the bare minimum needed to run. After that I would work on ISOLATED subsystems - that way they won't affect each other, so your code (shouldn't) break other code. Then I would fill each subsystem out to "working", although more like "working and safe", and then finally advance to "polish, enhance".