Not everyone spends many hours a day at a coffee shop like I do. Not everyone's brain blanks within the walls of an office. Not everyone has the honor of working with a strange population which also primarily exists within the coffee shop.
For these and other reasons, not everyone realizes there are unsaid rules, commandments, to abide by in the event that you visit 'our world'. Below is the beginning of that list.
Thou shalt USE headphones There is a reason your computer, iPod, or music device has a headphone jack. No one here is interested in listening to your music. If they are, they will listen themselves, on their own headphones, to the music you share on the local network. Otherwise, keep it to yourself.
Thou shalt not be power-hungry (don't hog the power) Look around you! Is there a power source near you? Are you plugged into it with your computer? No? Someone around you needs that power source. Don't hog the power source you aren't even using anyway.
Thou shalt drink coffee (this is not a free wi-fi cafe) Coffee shops have free wi-fi for their customers. Do not go to a coffee shop just to use the internet and not order anything, and NO, water does not count. No, it also does not count if the person you are with got something. Order something...especially if you are visiting an independent shop trying to keep up with the bigger chains.
Thou shalt wear shoes This shop may look like a living room...but it is not. You are gross. That is all.
What other coffee shop rules would you add?