Another way is to call the taxi hotline for the city in which you are traveling. I have done this several times, which has resulted in a) my full fare being reimbursed and b) the driver being sidelined for a day as punishment. You also should give the driver exact change! (somewhat obvious, but also worth it)

The only way to get back at a grouchy taxi driver without resorting to violence is to get out on the passenger side and leave the door open. He will have to get out and walk around the vehicle to shut it. A small victory, but satisfying.

I don't give him a tip, even if its only £1.99 I still take the penny.

dont do anything wihlst your in the ride, because he may try something like purposely taking a longer route or even raping you. wwhen your about to leave purposely give him all your change, that way he has to count every little penny.so if its £5.00 give it all in as small amounts as possible, making him wait and give him £.499 and not £5.00 that way he probably wont say anything but if he does you can laugh and say SO sorry i forgot your penny, one second. :) that'll patronize him and make him feel small if anythnig but!

Depends why he's being grouchy. Perhaps he has a lot of stress in his life. Perhaps someone has just been awful to him (whilst no excuse). If he is saying rude things, tell him you'd rather not chat, or ask him what's wrong. If he's taken you a long route say "I know you've taken a long route for where we were going, I can't really afford that kind of deception, but if you really need the money here you go". If it's really bad make a complaint to the licencing authority, but remember that we all have off days and sometimes it's better to break the cycle rather than keep it going. remember to always check that you are getting into a licenced vehicle (before getting in), and if you are worried phone a friend and tell them exactly where you are.