The best place to start with training is with the topic that is most relevant to your employees: the knowledge and skill that they need to do their job. I call this functional training. It can be as simple as training a new employee on your expectations for them and as complex as a multi-week engineering boot camp to bring new recruits completely up to speed on all of the historical nuances of your product.
The training courses should be tailored to the specific job. If you attempt the more complex-style course, be sure to enlist the best experts on your team as well as the manager.
As a happy side effect, this type of effort will do more to build a powerful, positive company culture than a hundred culture-building strategic off-site meetings.
No startup has time to do optional things. Therefore, training must be mandatory.
(1) This is new ground for me. As Ben wrote in Four reasons why you should train your team, “My personal experience with training programs at companies where I had worked was underwhelming.”
(2) Re. “It can be as simple as training a new employee on your expectations for them” — perhaps this is about clear communication more than “training”. The mistake we often make as managers is that we think we’ve communicated clearly, but we haven’t. Making the communication more formal, such as setting up a “training session”, is a neat solution.