DON'T - Be aware if you are on any prescription medication as some legal drugs in your country might be very illegal in the UAE!! Even if it's in your system make sure it's well out before you land if you get drug tested at the airport you will go to prison. They take hair samples at the airport...and heat detection.
DON'T- Show affection between men and women, any touching (hands even) in public is an offense and you will go to jail.
Men and Men are okay as this is a sign of friendship, and Girls and Girls as well.
DON'T- Swear in any language or make any rude guestures. Be polite and on your strictest well behaved behaviour.
DON'T- Drink alcohol anywhere anytime. be sure to confirm a location that's okay. If you have alcohol in your car and drive through a city that's got an alcohol ban, if your caught you will go to jail.