How do we leave Planet Earth as soon as possible?

1) Reusable launch vehicles for access to low Earth orbit.
2) Water mined from the Moon or asteroids pulled into low Earth orbit, made into rocket fuel.
3) Robotic construction of life's orbital infrastructure.
4) Populate by launching people and other life forms.

A lot of science fiction is set in a universe where people easily travel around the Galaxy, hopping star to star with the same level of effort that we today move from country to country. This is not realistic — the truth is that it would take a couple thousand years traveling at a couple thousand kilometers per second to reach even the nearest stars.

That would require a city plus artificial countryside, as well as artificial farms, forests, lakes, swamps, etc., together with thick cosmic-ray shielding and 2000+ years of nuclear fuel, all accelerated to a speed 100 times faster than the fastest man-made object so far built. This could only be a Stage 2 project, for a successor civilization with thousands of years of experience in orbital life.

But how do we get there? How do we get life into orbit?

Rule number one is to reduce the access costs. The two big ways to accomplish this are quick-turnaround reusable launch vehicles, and fuel depots in low-earth orbit. Then, once these technologies make it cheaper to launch, send robotic mining and construction machines to construct life's orbital infrastructure. Once that is done, populate with people and other life forms. Then repeat.

A small handful of companies are making good progress on reducing the costs of access to space, but the launch window is short. The efforts need to be increased by a factor of 10,000 or more. We need to start moving mass on a MUCH larger scale, and we need to start now.

The question is, how?