A guy in Bangkok told me to skip the airport taxi and take the bus for 30 baht
He walked me to the stop outside gate 3 and showed me which line went to Khao San for 30 baht instead of the 500 baht taxi. I've used local buses in six countries since then and saved way more than any travel app ever got me. What's the one cheap transit tip you got from a stranger that you still use?