1. Don't assume that something that is obvious for you may be the same for another person.

I remember hitch-hiking with two men from Kosovo once. I randomly told about how the death penalty was wrong. For me, it was granted. The man driving though said it should have been legal for those who evade taxes. This sparkled a small discussion with his nephew, who was the other man in the car. Luckily everything went well in the end. Great post!