It got me wondering if there were any concise, potentially catchy phrases that can prove useful in aligning everyone's thoughts around the core ideas of producing quality output.

None of them original to me, but I agree with all of them:

• You Arent Gonna Need It - Don't write code because you think you'll need it. Write it when you actually need it. Keeps the code simpler and so hopefully less complicated.
• Do The Simplest Thing That Could Possibly Work - if you're ever in doubt as to what to code - code up the simplest possible thing that will do the job. It's easy to make a simple system complicated. It's hard to make a complicated system simple. Get something simple down and incrementally add code and refactor.
• Don't Repeat Yourself (or alternatively Once And Only Once) - duplication is the root of many, if not most, maintainence nightmares so don't do it. Which leads us nicely to...
• Refactor Mercilessly - refactor all of the time. Any time you see duplication, lack of clarity, etc. fix it. Fix it straight away.
• Test First - write your tests before your code. That way you know when your code works.

My own personal mantra on software development has changed many times over the years. Currently it goes something like:

• Minimalism - Make the code/development-process as small as possible (but no smaller). Don't add code/process unless it is absolutely necessary. Before you add it ask yourself whether there is anything you could change that would remove the necessity of adding it.
• Tight Feedback - Make your feedback loops as tight as possible (but no tighter). Continually writing tests before you code is better than writing tests at the end of each week. Pair programming is better than a weekly code review. Failing fast is better than an error that comes long after the cause. Etc.
• Introspection - Look at what you do and how you do it. Try and make it better. Do this all of the time.
• Transparency - Make it obvious to everybody how everything works. Why does this code exist? Because of this user story. Why does this work this way? Because of this test. How close are we to completion? Look at this big visible chart of completed stories on the wall. Etc.

Unfortunately - that's hardly pithy :-)