Here is an little excerpt from a great interview with Imagineer Tony Baxter, Senior VP of creative development and the lead behind attractions like Big Thunder Mountain, Indiana Jones (Disneyland), as well as as many others.
I studied landscape architecture at Cal Poly and developed an idea for a Mary Poppins-themed attraction as a course project. A friend at Disneyland was able to get it to Imagineering where they passed it around. That led to a second, more in-depth tour of Imagineering. It was a reality check. They told me [my project] was pretty good for someone starting out, and then showed me the work that was done there. It was overwhelming, but it was sort of a kick in the can. As a result, I changed my career and school and went to Long Beach State to study theater design.
After graduating college, I applied at WDI [Walt Disney Imagineering, then known as WED--for Walter Elias Disney--Enterprises] and submitted my portfolio, which included an attraction I developed based on the film, The Island at the Top of the World. I had invested my entire senior year in the project. Ultimately, the film was not a hit--but I got the job.
I think Disneyland is unique, because it is theater and it uses a landscaped environment and architecture to tell its stories. So I was well versed in all three of those areas. It worked out well. I sort of stumbled into my profession."
Check out the rest of th interview here
Here are a few more interviews with Tony Baxter that are definitely worth a read.