Car tag is, as the name implies, the automobile version of the schoolyard game. It's a lot like tailing, or being tailed, except that there is little chance of your friends shooting you in the back of the head.
The basic premise of the 'game' (or 'deathwish', perhaps) is to take at least two cars, a dark night and suburbia and put them together. One vehicle will follow the other whilst the one being follow tries to 'loose' the follower.
It's a game I think we all play at least once when we get our lisence to drive. This explains a lot, because we're usually so young that we don't understand that we're putting ourselves in mortal danger.
There are a few things to remember when playing car tag. One, it's not fair to have the 'hunter' be a 3-cylinder Yugo and the 'prey' be an Acura NSX; by the same token, if the persuer is a passenger car and the persuEE is an SUV, it's not fair for the SUV to suddenly go off road where the follower cannot go.
Two, be careful. If you're seriously playing car tag, don't speed (too much). Keep alert for police, pets and CHILDREN. Nothing ruins a night of fun like a corpse. If the area a guaranteed free of cops, you can probably get away with not using turn signals as to potentially shake the persuing party, but don't say I didn't warn you.
Three, don't stay in the same area, especially over mutliple nights. This will anger the residents and may cause police patrols to show up more frequently there.
Four, consent. Do not follow random strangers. Make sure you only follow friends who are 'in' on the game. Not only is it rude and unfair to tail someone who doesn't deserve it, they might take you as a threat and, for lack of a better metaphor, 'pop a cap in your ass'.