How to ship a functioning (if rough) product, how to communicate effectively with other people (how to match your words to their background and experience), and how to value their time.
The first will make sure you can do work, the second will make sure that you can explain your work to other people, and the third ensures that you'll be paid well for your work.
The first will make sure you can do work, the second will make sure that you can explain your work to other people, and the third ensures that you'll be paid well for your work.