Always have clean ears. You never know when you'll be offered to share ear buds with a cute boy. (Thanks for teaching me good hygiene, Mom.)
I enjoy whistling as much as the next guy, but there's a time and place for it. And in a shared office in the work place is not one of them.
Don't lick foil containers. It doesn't matter how good the Laughing Cow cheese is. Or the yogurt. Don't do it. You're tongue will thank you.
Don't add celebrities — local ones or world-famous — as friends on Facebook unless you actually know them. It's just sad.
"Thank you" is always a good comeback. You will always sounds polite, even if you're also sounding condescending For example, if someone was to sarcastically say, "Wow, thanks for screwing that whole project up." You can say in return, "No, thank YOOUU."