It's been an interesting and successful experience thus far.
* A training schedule, similar to a degree plan in university - just something that outlines where the organization expects them to be at 3, 6, 9 and 12 months during their first year of employ.
* Coding standards defined by the organization. Telling any developer, but particularly a junior, that your standards are "I know it when I see it" doesn't fly.
* Formal code reviews. This is something we could definitely do better. I'm working getting Atlassian Bamboo to make the reviews easier on everyone involved.
* Regularly scheduled meetings with the trainers and the junior. We do every 3 months, with less formal meetings more frequently. It's important to let them know how they are progressing, and to give them tips on how to improve any deficient skill sets.
Overall, I think the most important thing is to maintain open lines of communication.