Ron Jeffries emphasizes two key practices for starting agile process:
1. Running Tested Software
2. Coaching and Training.
I've checked my experience and it seems Ron is absolutely right. In every team I start exactly from Test-Driven Developmet+Iterations and Trainings. Short and regular releases together with TDD greatly increase project focus and team productivity. While without training nothing will work at all. I never worked with developer who has been doing TDD before I showed him. I never worked with developer who knew XP before my team. That's sad, maybe, but training is a key.