[MrJohnston]

Here's what I'd suggest:
* As you approach a problem, never think "it can't be done." Instead, assume that it is possible and ask "How can it be done."
* Challenge all suppositions. Instead of shooting down thoughts and ideas because, "that's not how we do it," "I don't see that happening" or "It just won't work," ask "why?" And make sure that you understand why/why not.
* Yes, continue to improve your STEM education and skills. However, study and strive to understand all disciplines. Read great literature. Study art. Become familiar with history. Masters of other disciplines are great critical thinkers. However, they often have very different thinking "styles" than engineers. By improving your ability to think within other disciplines, you will greatly expand your personal abilities as a critical thinker.
* Strive to understand others' perspectives - even when you disagree with them. If you can think well enough to understand something you find "ridiculous," you'll be ahead of the game.
* Don't be afraid to be creative. Without creativity, we'd never invent new technologies. The creative thinkers on our robotics teams are extremely valuable during the design process as they often come up with brilliant ideas that would never cross an engineer's mind.