I remember a Dilbert comic where Dogbert decided he wanted to write down all the Unwritten rules of life. He could only come up with one.
Never call anyone past 10 p.m.
I’ll add…
Never ask a woman how much she weighs.
…So let’s collect as many as we can. A little guide book for life.
Never rinse out your pantyhose in the executive washroom, especially if you are a man.
As per the discussion in MPSIMS…
“Never date a good friend’s ex”
I’d also like to add…
Never use the urinal directly next to someone in the men’s room. For example, there are five urinals on the wall. Guy 1 comes in and takes the far urinal, guy 2 enters and takes the urinal at the other end, guy 3 enters and takes the urinal in the dead center, guy 4 enters and either takes a stall or waits for one of the other guys to finish up. Granted, there are extenuating circumstance where this does not hold true, but on a regular day, this is the norm.
I’m sure there are others. I could do the whole “don’t spit into the wind” thing, but thats just boring 
Let see, just off the top of my head … um
Don’t tug on Superman’s cape.
… and then there’s … um … oh! …
Don’t spit into the wind.
… and … let me think …
Don’t pull the mask off the old Lone Ranger.
… that’s all I can think of right now.
Oh yeah! Whatever you do, don’t mess around with Jim!
Holy crap! Did you plan that?!?! Are you reading my mind? Where’s my tinfoil hat??
the corolary to “never ask a woman how much she weighs” of course, is never ask a woman if she’s pregnant.
And if she is pregnant and you’re a nurse, never blab “Oh you know it’s a girl don’t you”.
No I didn’t, and we had planned to find out together when my hubby came with me next time!
And if you work in a clothing store, never, ever try to guess a woman’s size.
If someone lets you into a tight spot in traffic, or otherwise yields you the right-of-way, you wave or express a thanks in some nonverbal way.
That’s a biggie.
Here are two which are less well-known or agreed upon, but I wish more people played by these rules:
Don’t play one-upmanship when it comes to surgery, illness, or family tragedy.
Don’t tell new or expectant parents you hate their choice of babyname because it reminds you of someone/something hateful.
Thou shalt not kill. No one ever said you couldn’t do that, but its generally accepted that you don’t…
If you’re about to take the last beer, chocolate, piece of cake, etc, offer to share it. Don’t even consider taking someone’s last cigarette.
If you use the last of the roll of toilet paper, REPLACE IT.
If you see someone reading a book, don’t say “hey, don’t you love that part at the end where …”
If someone insists on picking up the check this time, give in gracefully. And then remember it for next time, so YOU can pick up the check.
Don’t tell an anecdote that happened to someone else as if it happened to you, especially if the other person is in the same room with you at the time! This just happened to me, at a party I heard someone telling a story that was familiar … it had happened TO ME and the person who was telling it was getting this great reaction … I was completely amazed at the nerve of this person.
I swear this written down somewhere…
There’s no sex in the champagne room…
There’s not?! Oh, crap…
Nope, that’s just a commonly believed myth.
Thanks to Delphica for reminding me of a big pet peeve:
If someone is reading a book and/or wearing headphones, please, please don’t sit down and talk to them! Generally, if a person is reading or listening to music you can safely assume that they DON’T want you to strike up a conversation with him/her.
Never bring your cell phone or 3 month old baby to a movie theatre!
Never wear white shoes after Labor Day or before Memorial Day.
Don’t double dip!!
No talking in the men’s room.
No eye contact either.
If you live in a smoking state, there is nothing wrong with playing “Sink the Battleship” in the urinal.
Don’t eat brownish snow
If you love something, don’t let it go. Ever. I mean, good god, are you insane? What an ego you must have that you think someone else will love you again?
Everyone masturbates
Monty Python quotes never get old.
Iced coffee is a tool of the devil.
There are three kinds of people in this world: those that are good at math, and those that aren’t.
Never use “damn, you guys are all boring sucky losers” as a thread title on the SMDB without first bending over.
There are starving children in Africa. Be sure to send them the half serving of rice and the tapioca pudding you didn’t quite finish tonight.
“How you doin’?” is not a good pick-up line.
Everyone is immortal until proven wrong through death.
Packets of Nerds and tea will NOT get you through the day (damn, I’m hungry).
You will never be on Who Wants to Be a Millionaire.
Never trust a tall man from Brussels when he offers you a vegimite sandwich.
Many people are profoundly unoriginal. The rest just copy off them.
Never tell a near deaf dog to “sit.”
“I just want to be friends” is girltalk for “piss off.”
Everything I ever knew, I learned from The Simpsons.
Everything you thought you knew is wrong.
You were dropped as a child, at least once.
Never, ever suggest that you’ve had better.
If you can cook, odds are your SO can’t.
The cop will be around the one bend in the road you’re not looking at.
and finally (for now),
No matter how wonderful you think someone is, somebody, somewhere is sick of their shit.