One of my professors once said:

"Disturbances have priority."

Even though the context was different I think it can be applied to (agile) development, too. How?
Development is a team effort and every programmer has to be creative - in the sense of "creating code" and "finding a simple solution". Everything that disturbs this individual and group effort has to be focused on and eliminated forever.
Example: If you find that the old static libs give you trouble (some search paths missing, lost headers, conflicts between version etc) build a framework once and put it under SCM. The trouble will vanish. Otherwise development time is spent on fighting those disturbances over and over again. Once they pop up find a solution that will work.

I wrote some recommendations on books I like and find useful.