RULES OF ETIQUETTE

Please, ALWAYS, ALWAYS, ALWAYS assume a no-show and bring enough money to pay by yourself, or enough time for alternate arrangements. There is no guarantee, express or implied. People may fail to show up for a number of reasons, many beyond their control.
Leave plenty of time to get to the airport. This varies by time of day and location within the City, but generally doesn't exceed 2 hours in Manhattan, even during rush hour. If you are not sure, consult those who live nearby. If you've never done it before, estimate conservatively! You never know when construction or visiting dignitaries will add to the fun.
For now, rides are expected to be 1 person per party, up to 3 parties per ride.
Even the most punctual traveler can use a reasonable windo of opportunity. In order to maximize the probability of connecting, we suggest arrving a few minutes early, and planning to wait up to 5 - 10 minutes past the departure time. Being more than five minutes late, however, is considered pushing it.
Be aware that only so much luggage fits in the trunk of a cab.
If you're going to two terminals, add tolls, then 10% tip, and divide by two where the first person gets out. Give it to the other person, not the driver.
2-hour rule: If no one has joined your ride within 2 hours of departure, it's acceptable to make other arrangements without cancelling as it's understood you may not be near a computer (although it would be best if you do cancel). If you join someone else's group within that time-frame, they are not obligated to wait, whether or not if they find out (via text message, etc). In other words, you are welcome to join a ride at the last minute, but the other rider may not show.