who are you driving with? because none of these suggestions matter if the person you are driving with is a shitty trip companion. besides that -
audiobooks, or magazines in audio edition, or lectures, or whatever, are a must have, as are headphones and separate musical devices for everyone participating in the drive. on my road atlas i also have written down radiostations that are worth listening from oregon to georgia. sometimes everyone has to participate, and some classic rock really does that.
snacks i always take: cheese, grapes, soymilk, ritz crackers, emergence-e packets and bottles of water, several thermoses of my coffee, and a pack of cigarettes for every two hours you're expected to be on the road, or plenty of loose tobacco. there is nothing worse than finding yourself on some shitty abandoned state high way with no cigarettes for hours.
make sure you know what you're driving into, weather wise. if there are any girls on the road with you -- don't bother with much. put your hair in a braid and leave it. there is nothing that's going to stand up to 12+hours of variable weather and wind besides a braid. if you really fucking have to, that spray shampoo in a can. also, layers.
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i try to time my trips around full moons. especially if you're driving through indian nation, the new moon can be frightening and disorienting. i'm serious. oklahoma and kansas and idaho in pitch black is some horror movie fucking shit.
as for driving - comfortable shoes are a must. is this your normal car? are you used to it? do you know what works and what doesn't? figure all of that out right now, and not while you're on the road. if you have knee or foot or back problems, appropriate brace or splint or whatever you need to do about it. when you're driving, keep your window cracked. the blast of cold air kept me awake and focused. and don't be afraid to stop, jesus christ.
12 hours is really the max for most people, and shit starts to go pear shaped around hour 12. i drove from denver to arkansas in one stretch, and there was a point in kansas where the sky, the road, everything was the same shitty grey colour and it was lightly snowing. i knew i only had one more hour to go, but i was afraid i would start doing that pilot thing where they can't figure out what is up and what is down. i pulled over, stretched, drank some coffee, and just stood in the cold for half an hour. if i hadn't, i think i would have killed both myself and my mother.
i don't know how much you believe in the old ways or anything like that, but i took everything i saw on the road extremely seriously. i was in texas and the whole car (my mother, my two little sisters) were asleep and i had to pull over for a piss. i was so tired and it was so late and it was so flat and dirty and dusty. i pulled over and got out of the car and was so happy it was warm! i turned around and as far as i could see was on fire. i don't know if it was a lightning strike or arson or what, but the moon was all bloody and the fire was so so hot. i screamed and ran back into the car and made my mother drive. i was a psychotic mess until we got out of texas, even my sisters couldn't relax me. when we made it to new orleans i immediately went looking for news about it. turns out a whole family burned alive in their house, and it caused car accidents when it spread across the highway. i don't know what i'm trying to say, but if something doesn't feel right, don't question it and get back on the road. as a non white southern girl, this can be life saving advice.
i like to take the same routes for certain drives. i keep a sharpie on me for this purpose - kinda like a train bum. there's this one rest stop outside wichita which i've been to at least a dozen times, and i always make sure and make my mark and date the bathroom stall. stupid, but it's tradition and i'm not going to stop now. i also take a lot of religious stuff with me, little tokens. my mom's buddhist prayer beads she gave me, my book of saints, my little st. catherine of alexandria prayer card. my sister likes to bring the same bandana every time. some token of comfort is nice.
i've only flown 3 times in my life, but i've gone on 30 or more 12hr+ road trips. it's honestly my preferred way of travel and it kills me that it's now basically cheaper to fly.
eta: RedLeader, isn't it great that we live in America? you are going to be able to see so much of this fucking amazing country. I think we forget, because we are Americans, that this country is massive. Gigantic! Foreigners should be jealous of all the different places we pack into our country. Rain forests and swamps and deserts and all kinds of shit. make sure and take pictures. also, you will never be bored. it's impossible. there is too much to see, and too much to learn about the people in the car with you to be boring. they'll be downtime, sure, but not boredom.