Of the four project development variables - scope, cost, time and quality - quality isn't really a free variable. The only possible values are "excellent" and "insanely excellent", depending on whether lives are at stake.

Make it work, make it right, make it fast.

Code wants to be simple... I had to give up the idea that I had the perfect vision of the system to which the system had to conform. Instead, I had to accept that I was only the vehicle for the system expressing its own desire for simplicity. My vision could shape initial direction, and my attention to the desires of the code could affect how quickly and how well the system found its desired shape, but the system is riding me much more than I am riding the system.

I mean, source code in files; how quaint, how seventies!

I tell people to start implementing when they are pretty sure there aren't more important stories out there. An iteration's worth of data is worth months of speculation.

I've known people who have not mastered their tools who are good programmers, but not a tool master who remained a mediocre programmer.

If testing costs more than not testing, then don't test.