How do you train admin to think critically instead of just following a to-do list?

When I hired my first virtual assistant to take on some administrative tasks that run the business, it took me about 6-12 months to find the right training and tools to teach him how to do the processes. 

realized that I didn't just want a worker waiting on a todo list everyday, but I needed someone who could make critical thinking decisions. And then my training changed from to do lists, to showing him how to think and why, and allowing him to make some decisions to build his confidence and trust. 

Do any of you have any training tips for your admin staff to strengthen the processes?