Have just been talking about the agile manifesto.
The full works is here:
but I like these principals from the principals page:
Continuous attention to technical excellence
and good design enhances agility.
Simplicity–the art of maximizing the amount
of work not done–is essential.
The best architectures, requirements, and designs
emerge from self-organizing teams.
At regular intervals, the team reflects on how
to become more effective, then tunes and adjusts
its behavior accordingly.