Since I had been GMing the adventure path Carrion Crown for my game group I develop a series of superstitious behaviors the illiterate commoners of Ustalav would have towards humanoids and which can be source of quite hilarious and interesting situations. I hope you enjoy them:
-Comb the beard of a dwarf during twilight will grant you success in trades or make your business prosper.
-Forcing an aasimar laugh loudly trough tickles will grant you an abundant crop next year.
-Kissing the hairy part of a halfling's foot would grant you a safe journey if you have to go to another county.
-Steal a feather from a tengu and use it as a quill for your notes will prevent you from flunking (this is mostly done by the mothers of the university of Lepidstadt students).
-Pulling or pinching the ears of an elf or half elf will cure you of impotence or erectile dysfunction.
-Grab the tail of a tiefling and count to five before let it go will bring five days of intense diarrhea to your enemies.
-Kissing a half orc during a full moon night will prevent you of being attacked by monsters until next full moon.
Feel free to share any superstitions of your own concerning not only the people of Ustalav but also those of other nations of Avistan.
Not G based, but:
Mutual bows of greeting and departing with an Elf means good luck.
Always charge lees to halflings in case they're fey in disguise.
Dwarf shoed horses work better.
Elf blessing on babies.