1) Consistent but evolving paradigms. In other words, let's not be static, let's keep most change happening relatively slowly. But let's review and try to fix problems as they happen, cleaning old code slowly and continuously.
2) Try to document everything to at least a basic extent.
3) Let the documentation practices evolve. Don't try to document too much too soon. Start out with a basic level. As the project matures you will have a better idea of what needs more documentation and you can spend your time on the areas that help.
4) Don't underestimate person to person mentoring.