Never walk underneath a ladder propped against a wall. It's bad luck. That's because the gods hate trying to work out the square of the hypotenuse enough as it is without you trundling along and bisecting the base line measurement with your silly shoes. It'd also be pretty grim having to spend eternity in damnation just because of a geometrical mishap.
Don't put food in your mouth using a knife. It'll make you look as if you missed out on the 1966 casting session for One Million Years BC (whether or not you resemble Raquel Welch) and may give any younger siblings in the vicinity the urge to accidentally jog your elbow. And forked tongues only look good on snakes.
Birds of a feather flock together. Except when they don't.
Never accept lifts from strangers. Aunty Barbara did that once in the seventies and she's never been the same since, what with the tattoos and the piercings and the CND posters. At what point an acquaintance ceases to be a stranger is a moot point: a decade sharing a house and / or bed is usually enough, but you can never be too careful.
If you wash your face in the dew at dawn on the first of May, you'll be beautiful all year round. If you get up early enough, don't stand on the dog in the dark and once you've got rid of the grass stems and ants from your hair.
Good things come to he who waits. If your good thing hasn't arrived yet, you've just not been waiting long enough or you gave the wrong address when you were ordering the good thing. Don't forget that patience is a virtue. Virtues are good things too. See, now your good thing has arrived already even without it being the actual good thing that you expected.
What doesn't kill you makes you stronger. As proved repeatedly using ducking stools during the witch trials of the middle ages, a witch who drowned was innocent all along. Thus being both strong and dead. Or in other words, what will be, will be. If you allow fate to take its course, then that is the course you were always fated to take; if you make a conscious act or a change of direction, then that is the course you were always fated to take... Ok, you're always on a winning streak with the fate thing.
Rain before seven, fine by eleven. Unless you're very unlucky and the storm lasts longer than four hours. Quite what climatic calamity would be unleashed for the next forty days by rain before seven and after eleven on St Swithin's Day (July 15th) is anyone's guess. So be prepared and take an umbrella.