Scale up or scale out?

Listening to the questions, from the audience and conversations after, one thing was clear - this is a complex challenge that even smart, experienced people struggle to do well.  When moving toward developing software in a parallel environment, there are a lot of things to consider, a lot of questions come up.

How do I train my developers? 
Can I reuse what I have or do I have to rewrite?
What tools should I use?