https://medium.com/the-mission/first-principles-and-the-art-...
tl;dr --
1) Reduce the problem to a question answerable by a hard science like physics, chemistry, or biology, and pay attention to the theoretical limits.
2) If you can, find data on related industries and see if you can find long term trends. (Example: http://rameznaam.com/wp-content/uploads/2015/10/Lithium-ion-... )
3) Extrapolate into the future.
4) Think of some way to exploit the information you've uncovered to gain a market advantage.
Other helpful techniques: Is there an industry which is subject to some form of bureaucracy which is distorting the market? How can technology be used to disrupt this?
Honesty has phenomenal draw in marketing when the recipient agrees with the message. Even if one's disagrees, the product is harder to attack when everyone around it is honest.
One of the challenges will be building out underground habitats, and establishing mining for critical resources. Gaining experience with how to do that efficiently here on Earth will make it easier to set it up on Mars.
Furthermore when you start colonizing Mars, you're going to want high speed transport between locations. Rockets will work, but are wasteful. Airplanes don't work with thin atmosphere. But a hyperloop will.
So let's learn how to bore hyperloops cheaply and efficiently. Prove out the technology, make it repeatable. Then when SpaceX is ready to take us to Mars, we arrive with key pieces of technology that we'll need to colonize it.
The scope of his vision is breathtaking.