I added his book Embracing the Wide Sky to my queue after reading his Q&A with Jonah Lehrer back in early 2009. I finally got around to picking up a copy recently, and it did not disappoint. It is a delicious mix of philosophy, science, autiobiography, and practical advice. It has chapters on intelligence, language, perception, and creativity among others.
Here, for example, is advice on how to think:
Use your imagination as much as possible, especially in "thought experiments" that force you to think about the consequences of something being true.
Perhaps most important, treat each new piece of information you read or watch or hear as a potential piece in a puzzle, rather than simply as an end in itself. Acquiring information is not the same as learning, or thinking, or living for that matter. Bits of information are what we use to build reflections, evaluations and understanding in our minds. Like each one of us, these dots of data make most sense when they contribute to something greater than themselves.
For an outside (and somewhat clichéd) perspective on Tammet, check out the 48 minute documentary "The Boy with the Incredible Brain" or this 60 Minutes profile. But you really must pick up the book to get a richer, more personal perspective of how his mind works.