Robert Downey Jr. and Zach GalifianakisAh, the road trip; a cinematic rite of passage that takes best friends, estranged family or mortal enemies on unlikely journeys in search of love, enlightenment or the perfect buzz.

Todd Phillips' 'Due Date,' opening this Friday, is the latest in a long line of great American road trip movies, a manic mash-up of 'Planes, Trains and Automobiles' and 'The Hangover,' with Robert Downey Jr. and Zach Galifianakis as two unlikely traveling companions forced together by bad luck and Galifianakis' own ineptitude. Downey is a father-to-be, trying to rush back home in time for the birth of his child, while Galifianakis and his too-friendly dog, Sonny, are on their way to scatter his dead father's ashes at the Grand Canyon -- as you can imagine, mayhem ensues.

In honor of 'Due Date,' we've composed a list of the top 7 tips that any aspiring road-tripper needs to remember in order to have the best (or worst?) journey ever. So stock up on your drugs, get your motor running, and hit the road with us.
Midnight Run Movie Poster
Midnight Run
Based on 16 critics

When Eddie Moscone (Joe Pantoliano) hires tight-lipped bounty hunter Jack Walsh (Robert De Niro) to locate... Read More

Due Date Movie Poster
Due Date
Based on 39 critics

Peter Highman (Robert Downey Jr.) will be a dad for the first time when his wife gives birth in five... Read More