When playing the license plate game, only personal vehicles are allowed. No tractor trailers. RVs and motorcycles are a grey area.
When possible, route your trip through a state capital and/or national park and make at least one passenger wake up or quit playing iPhone long enough to get out and pose for a photo.
When in Texas, route your trip through as many county seats as possible. That way you can photograph the county courthouses. Human subjects optional.
Even though kids don’t want to get off the seesaw and the ice cream will melt, make everyone line up for a photo at family gatherings. If the cousins from five states over are present and the VW-camper enthusiasts are back from Eastern Europe–at the same time!–you’ll want to remember that.
On successive days of a car trip, rotate seats. This is hard to do with the newfangled car seats. On successive nights in hotels or relatives’ homes where beds must be shared, rotate who has to sleep with the One Who Kicks.
Keep your hat on when rolling underneath a barbed wire fence (it’s common sense really).
Eat an ice cream. Or two.