Don't Check a Bag
This the first and most crucial principle of minimalist travel. By limiting the number of bags you bring on your trip, you will automatically be forced to pack smart and light to fit your essentials. Not only does not checking a bag limit the amount of stuff you can lug around, but it also saves you valuable time.
When I'm traveling, I want to maximize the amount of time I have to explore and enjoy my destination. A checked bag equals more time spent at the airport and less time spent actually traveling. If you aren't carrying tons of stuff around on your trip, it's much easier to move quickly and be flexible with your plans. If you brought everything and the kitchen sink, it's much harder to catch that crowded bus in Peru or hop on a motorcycle in Vietnam.
There are of course exceptions: if you are going on a surf trip you will need to check a surfboard. However, as a general rule of thumb, if you only have one bag and a small backpack, a whole world of possibilities remains open.