Purely trial and error. The day I drove into Mexico I had no idea, and I just made it up as I went along. 55 countries later through Latin America and Africa,

Purely trial and error. The day I drove into Mexico I had no idea, and I just made it up as I went along. 55 countries later through Latin America and Africa, and I've become fairly good at it :) I made a couple of videos lately to teach other people how to do it: https://www.youtube.com/watch?v=IOljPXY0Smg https://www.youtube.com/watch?v=IOljPXY0Smg https://www.youtube.com/watch?v=qdQPz0I-Mgc https://www.youtube.com/watch?v=qdQPz0I-Mgc