What a great concept, I've been looking for a resource to collaborate with fellow SEs.
It's funny because I used to use the 'wing it' strategy when starting out. I thought the calls would go well, but then when my manager shadowed some calls I realized the opportunity that I was missing out on. He would ask questions like "Ok, who is deciding on this?" "What are the next steps?" "What is the customer's role in this project?" "When do they need the solution implemented?" etc. Taking the time to set goals and call prep has been invaluable and I highly recommend it because you get more out of the time on calls with customers.
How do you guys structure your call prep? How detailed do you get?