This is a common tourist mistake. Flag the taxi, and then get in the car, say hello, then tell the driver where you are going. Only tourists think they need permission to get in the car, and so the drivers will refuse them. Tourists also tend to request unprofitable routes, like going 15 blocks in Times Square.

They are allowed to turn the off-duty light on, and to get one final fare going their return direction at the end of their shift. This rule is coming to an end because the GPS logs have proven that the drivers abuse this rule extensively.