- short iterations
- collective ownership
- pair programming
- avoid premature optimization
The biggest problem with the simplicity principle is that people often disagree on what constitutes "simple", and I've always struggled to come up with a definition of simplicity that was, well, simple. I came across a quote today that I think sums it up pretty well, from Antoine Du Saint-Exupery.
Perfection is not when there is no more to add, but no more to take away.