Always grab the dashboard or doorhandle and yell "Whoa!"
Always tell the driver to slow down or speed up.
Constantly remind the driver of road conditions.
Whenever possible, adjust all the dashboard controls, including the radio, heat, and fan.
Remember: If there is a mirror on the passenger side door, it's there for the passenger. Feel free to adjust it at will.
When at a traffic light, inform the driver the millisecond the light turns green.
Remember your religion; always yell something like "Jesus", "God", "Allah", etc.
The more upset you become, the more words you should add to the All Mighty's name. For example: (and with NO offense meant to Jesus, so please, NO flaming email!)

* A car simply pulling out in front of you, calls for a "Jesus!"
* A car pulling out in front of you and hitting the brakes, calls for a "Jesus Christ!" and
* A car pulling out in front of you, hitting the brakes, and then making a sudden sharp turn in front of someone else, calls for a "Jesus Christ, All Mighty, what the @#$#% is this a*%hole's problem??!!!"

When giving directions, tell the driver to turn after you pass the intersection.
Point to the left and tell the driver to make a right.
Point to the right and tell the driver to make a left.
When giving the driver directions, always mean to say one thing and tell the driver another. Then when the driver gets confused and passes a turn, yell.
When riding with other passengers, quickly jump in the front passenger seat and yell "Shotgun!" Then, tell everyone you'll sit in the back during the return trip. But, have no intention of doing so.
No matter what lane the driver is in and where you are going, always tell the driver that we would be better off in the next lane.
When in the middle lane in heavy traffic, tell the driver that you really need to be in the right lane. Then when you finally cut another car off to be in the right lane, tell the driver you made a mistake and that this lane is going to end.
When traveling straight, tell the driver to get into the left lane. A lane that suddenly becomes a "left-lane-must-turn-left".
Every time you see a car pulling out, yell to the driver "Watch it!"
Make sure that you put your chewed bubble gum into the ashtray, unwrapped.
When being picked up as a passenger, bring a messy powdered sugar donut and a large uncovered cup of coffee. Then, piss and moan whenever the driver hits a bump in the road.
All passengers should pretend to have their own brake pedal.
Grab the steering wheel if you feel the driver can not deal with a traffic situation.
When directing the driver to make a left turn, tell him to make a "You-turn". When directing the driver to make right turn, tell him to make a "Me-turn".
As a passenger, feel free to take your shoes off and smell up the whole car.
Whenever the driver parks, get out and inspect whether or not the car is properly parked within the lines.