• Work less
• Consume less
• Travel less
• Enjoy things that cost few resources, such as talking/hanging out, reading books, playing games

For any type of fast transportation through earth's atmosphere, drag (air resistance) will be important. The drag force is roughly proportional to the velocity squared, the surface area of the moving object and the air density. So assuming we won't have Hyperloops any time soon, we should move slowly, with a small surface area, ideally in a vehicle with a small drag coefficient. Some simple ways to make travel more energy efficient are:

• Reduce the maximum speed of cars to say 60 km/h
• Make much smaller and lighter cars, as they don't need to be as safe
• Make public transport cheaper and slightly faster than cars for average trips
• Increase the cost of flying and tax fuels for planes similarly as fuel for cars

• Earth's population probably shouldn't grow much larger than it is now.
• Make contraception free of charge everywhere.
• Provide tax or financial incentives for sustainable family sizes – depending on the region/country.
• It's not only about the number of people, but also about how many resources are consumed. I'm pretty sure we would all happily fly a helicopter or private jet if we were able to.

• Invest in solar panels around the equator, where they are most efficient. Also invest in ensuring stability and prosperity for the countries where the panels are placed.
• Invest in a high-capacity power grid to transport energy over long distances.

• Plastics: use standard shapes and compositions for easier re-use and recycling
• Lower taxes on repairs and maintenance, higher taxes on non-sustainable production of new goods