1. make it a requirement.
2. make it sexy: give a lot of airplay, kudos, and social status to those who do a good job teaching.
3. give bonuses for senior faculty teaching freshmen courses
...and before they become "senior faculty"
4. don't hire assholes...to begin with. At UC Berkeley there were a couple of senior professors who always made it a point to teach freshmen: Alain Renoir and Julian Boyd immediately come to mind.
5. make it an important part of tenure review
Joanna B.