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.

1. Avoid planes (and possibly trains and automobiles)
By movie logic, any time you've got somewhere important to be -- whether it's the birth of your baby or a Thanksgiving dinner with your family -- trying to get there the easy way is doomed to failure. If you attempt to get on a plane, you're at the mercy of delays, rerouting, or a fat guy rubbing his belly against your face and sending you into an apoplectic rage that gets you put on the No Fly List. Then, of course, there's the possibility of the plane crashing -- to quote Charles Grodin's immortal pre-flight freak-out in 'Midnight Run,' "These things go down!" Save time and rent a car (or, seemingly the most reliable form of movie transportation, a motorbike).



2. Never travel with children or animals (or Zach Galifianakis)
We've already established that Zach Galifianakis (who stars in two of Todd Phillips' road trip masterpieces, 'Due Date' and 'The Hangover') is pretty much the worst travel companion in the world ... but children and animals can come a close second and third. Road trips are meant for grown-ups, and when you add precocious kids like Abigail Breslin ('Little Miss Sunshine') or other creatures -- like the snakes in 'The Darjeeling Limited' or 'Road Trip' (another Phillips classic -- we're sensing a theme!), trouble is bound to ensue. Of course, if you travel with a monkey, like Jay and Silent Bob, she might just get you out of a sticky situation or two.


3. Have a steady supply of hallucinogens
An amazing number of road trip movies involve either the quest for drugs, or, at the very least, light-hearted indulgence in them. Could Jay and Silent Bob have had the wherewithal to defeat the Hollywood movie studio trying to steal their likeness rights with Bluntman and Chronic if they hadn't had their "doobie snacks"? Could Dennis Hopper and Peter Fonda have discovered themselves in 'Easy Rider' without the use of a little medicinal assistance? Hell, 'The Hangover' never would've happened at all without a creepy interloper deciding to roofie his new best friends. And don't even get us started on 'Fear and Loathing in Las Vegas' -- drugs may be bad, kids, but a road trip movie without them would be way worse.

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4. Get by with a little help from your friends (not your family)
No one wants to be stuck in a camper van full of neurotic family members, or to accidentally hit on your pre-op transsexual father because you think s/he's a kindly Christian social worker (yeah, 'Transamerica' was a definite eye-opener for poor Kevin Zegers) -- travelling with family is way more stressful than it's worth. Road trips were designed for BFFs; college friends trying to discover themselves, like in 'Eurotrip' or 'Road Trip'; or two women trying to escape their mundane lives like 'Thelma and Louise' -- although we wouldn't recommend ending your travel experience by driving your car off a cliff. It's kind of a downer.

5. Have some back-up cash
Regardless of how well prepared for the trip you think you are, chances are, you're going to run into money trouble. Whether you get your cash stolen while you sleep, end up melting your credit cards, or giving it all to a pair of greedy mechanics who don't actually fix your car ('National Lampoon's Vacation' -- Chevy Chase is a very unlucky guy), you're probably going to need a back-up supply. We suggest strategically placing wads of cash in various parts of your clothing, or, failing that, you need to get very comfortable with the 'Jay and Silent Bob Strike Back' method of offering "favors" in exchange for rides.

6. Costume changes are a must
No-one likes to wear the same underwear for a week at a time, it's just tacky, and a little antisocial of you. When preparing for a movie-style road trip, make sure to pack enough clothing for at least a week, possibly two, since it's inevitable that any journey will take you twice as long as you're anticipating. If you're having trouble fitting all of your outfits into one suitcase, we suggest that you take a page from 'The Adventures of Priscilla, Queen of the Desert' playbook and invest in your own bus, preferably painted pink, in order to stow the many glittering wardrobe changes that you're going to need on your journey.



7. Never antagonize the clerks
When you're tired, frustrated, or stuck with Zach Galifianakis (or his '80s/'90s equivalent, John Candy), it may seem tempting to take your aggression out on the hapless car rental clerk or check cashier -- but this plan will always backfire on you. Either the rental clerk will tell you that you're screwed and refuse to help you, or the check cashier will ... well, you'll have to go see 'Due Date' to witness the consequences of that, but needless to say, you catch more flies with honey than vinegar, weary traveler.

There you have it -- Moviefone's top 7 tips for surviving your very own road trip. Got any suggestions we missed? Share them in the comments below.



[Follow Laura on Twitter @LauinLA.]