ICE vehicle drivers, what do you do to prepare for a major road trip?

Oil change, check tire pressure and tread (including spare), check the cabin filter and washer fluid, make sure my portable jumper is charged, clean out and wash the car, pack a bunch of snacks I can easily eat while driving, make sure I bring a small garbage bag, appropriate cold weather clothing if applicable in case you have to walk somewhere.

That's already overkill but beyond that is just general vehicle maintenance regardless of any road trip. Just make sure any noticeable issues that affect the feel or sound of your engine/brakes/transmission/wheels are addressed beforehand.

There's really no reason to expect any vehicle will randomly break down over 300-3000 miles of mostly highway driving if it hasn't shown any signs of issues on your commute. The most common stuff like a flat tire you can't prepare for, you'll just have to deal with as it comes up.

My car is new enough the only thing I worry about is tire pressure and oil level/cleanliness. If I'm close to needing an oil change I'll get that done.

Tire pressure is key for MPG and you want somewhat fresh oil for obvious reasons

I dont drive anymore but did drive 8 years, mainly around Fennoscandia and Europe, once went to russia.

I made sure I have a good amount of audiobooks and podcasts, some basic food stuffs, water, washing cloths, soap, toothbrush and a good amount of extra clothes, especially boxers.

If I went with a lorry that I hadnt driven before or in a long time, I did a check up on the vehicle before setting off. Check fluid levels, checked the service history, made sure all tires are inflated properly and no bolts missing, check under the lorry and trailer to see if theres anything loose or hanging. During the winter I made sure I had snow chains.

Check tire pressure and oil change if it needs it and pack water. We buy food on the road although I might take along some fruit.

I drive old vehicles (average 15 to 20 yrs old) and do most maintenance myself so I usually bring along a full set of tools just in case, but Ive been surprising lucky with no breakdowns in the last few years. I usually buy vehicles with a really good reliability rating and currently drive an 03 Toyota Sequoia and a 05 Honda Pilot and both have been very good to us.

We have Canadian Auto Association if we really get stuck and the only time we've really needed it is when our 40' diesel pusher RV broke down (twice). A tow for that beast takes a semi truck and trailer and a short tow is $800. A long tow is more like $2000, so its saved our pocketbook a LOT of money for the $250 RV membership cost.

We're about to do 1000 mile round trip towing our boat so going to get new tires on the trailer right now. Nothing more depressing than blowing a trailer tire in the middle of nowhere.

Last summer, I drove around 2400 Km (I think that's about 1500 miles?) alltold. I have an old car (20 years old).

I did an oil change, since I would have hit the recommended kilometers during my trip. Made sure all the fluids were full and that I spares (especially coolant, since I've had issues with overheating and it boiling off...), made sure the AC was filled and working, gave the car a wash.

For the trip itself, I made sure I had water to drink, as well as some energy drinks and flavoured drinks in bottles that I could handle one-handed, rather than normal twist tops. Didn't pack food, but I did make sure to have some nut bars and trail mix (nuts and raisins, basically). Looked for some playlists and made sure I had offline copies of the maps.

I always carry a toolbox with me, as well as starter cables and small misc stuff - some zip ties, whatever the metal hose clamp things are called, some rags and some all-purpose wet napkins. Also toilet paper, because sometimes you gotta go and there's nothing, or the rest stations have toilets but no paper.

This might or might not apply, depending on where you are in the world, but I have an ADAC membership - it means that in most (all?) of the EU/Europe, I can get my car towed to a mechanic and possibly get some repair work at no cost. Or I pay and get reimbursed... not 100% sure, haven't had to make use of it outside of Germany. In Germany it's free towing, but also free roadside repairs if at all possible. I've called them a few times - dead battery, frozen door (in the open position, which made the first turn I took that day extra exciting as the door swung open...) and broken windshield wipers on a super-snowy day. They always fixed it on the spot and I could drive away. 100% worth the money. If something of the sort is an option, I'd say definitely grab it - even just 1 month or two or however long.

Generally I will:

• Check tires for proper inflation. This information is sometimes listed on the door of the car, in the part between the outside and inside, around the edges.
• Verify my last oil change is within limits.
• Check windshield wiper fluid. If needed, change out my wiper blades for new ones.
• Clean my windows.

But pretravel at home:

• I bake a loaf of bread the night before. The day that I am leaving, I will make sandwiches.
• Go to the grocery store and buy any food that I would buy at a gas station in the store instead. Junk food (chips, candy, trail mix, and healthy food (baby carrots, celery, apples, bananas).
• I prepare make-shift ice packs. I have a foodsaver and I made a few that go into my lunch bag/cooler. It is typically just a salt water mixture since it is colder than just ice.
• Pack a cooler with all the food and drinks that need to be cool.
• Prepare a reusable grocery bag with all my warm snacks.
• Pack my brita water filter pitcher so I can have tasty water in the places that I stay.
• Lay out comfy clothes and shoes for the drive.
• Check on google maps where all the rest areas are.
• Check google maps for expected travel time. For example, if I know I am leaving at 8:00 AM the next day, I will check the time the previous day at 8:00 AM. You can also tell Google your expected start time and it predict, but I find this is better real-world estimate.
• Check weather along the route to make sure I am not driving into a potential hail storm

The only stops I make are for peeing, filling up the gas tank, and taking short walks. Depending on the part of the country you are in, rest areas might be available, and some of them are actually very nice! I enjoy having a picnic at the nice ones.

Are you driving through the Australian outback or Alaskan wilderness or something?

I do basically nothing but pack the car and have an audio book.

I even do minimal stuff with my EV. I just make sure it's fully charged and check where the charging infrastructure is.

One thing people miss is checking the pressure on their spare tire. Give that check, you most likely will need to fill it. Also check your owners manual to see how to use the jack in your vehicle if you have one. If you never changed a tire before watch this video from Dad, how do I... https://youtu.be/0KDMdYww4VE
Edit: A note on spare tires. You will normally have a compact spare thats smaller, needs a high air pressure, and LIMITS your maximum speed on the road - normally 55 mph. Thankfully this is printed on the tire 90% of the time. Read what the tire says and check the owners manual. If you're lucky enough to have a full size spare you can just slap it on as long as it has proper inflation and go on your merry way like nothing happened.

A PMCS on your regular vehicle should be done, well, regularly.

Walk around the car while it's turned off. Look at the tread on each tire. Turn the car and lights on. Put on the hazard lights and walk around again. I used to do turn signals separately but it's all controlled by computers these days but if you've got an older car it's good to check them independent of the hazards. Get someone to step on the brake and make sure both lights illuminate. Cycle your high and low beams. Check washer fluid and oil level.

If you're non mechanically inclined, probably can stop there. If something else breaks it's gonna be over your pay grade. For peace of mind you can lay on the ground and look under. If anything is hanging too low, go get it checked out.

I used to make semi regular drives between Colorado and Montana when I was in college, so I got a system down for long drives early:

• map out the route and make note of what towns are at or around 1/2 a tank of gas' distance, there were quite long stretches of rural, non-interstate highway Wyoming with no services for hours, and poor cell service, so I never wanted to get below a half tank of gas at any point. Especially in winter where unexpected road closures or just poor conditions could turn a 9 hour drive into a 20 hour one, this saved my ass many a time.
• Make sure I have some podcasts and Spotify playlists downloaded to my phone's local storage; again, poor service along many stretches of that drive on every carrier make this a necessity, since there isn't going to be much for radio in those areas either.
• Go to Costco and get my road drinks/snacks ahead of time, saved a lot of money on gas station food.
• While at Costco, grab some motor oil (and windshield washer fluid, if in winter)-- this is a newer addition, as my current vehicle burns oil at a known rate (if you have had a Toyota with a 1zz motor, you know), so I just top my oil off at my refueling intervals. Not relevant to anyone else unless it's something you know is an issue with your specific vehicle, though.
• Check tire pressure and top them off
• Make sure my combo jump starter and air pump is fully charged the night before.

Hasn't failed me yet so far.

This might not be the kind of advice you're looking for, but as someone who is also not very mechanically inclined: CAA roadside assistance has saved our asses a bunch of times over the years. So I would highly recommend looking into getting a membership at a similar association in your country that also offers roadside assistance and/or road trip accident assistance coverage.

https://exchange.aaa.com/international-travel/international-clubs/

p.s. Also, if you don't have one already, I highly recommend putting together a car emergency kit for yourself:
https://www.getprepared.gc.ca/cnt/kts/cr-kt-en.aspx

I used to bring parts that were more likely to fail, tools, fluids, duct tape, zip ties, etc along with me. Modern vehicles are so reliable I don't really do much to prepare.

Make sure I have a current insurance certificate in my vehicle. They expire at weird intervals and, while I can easily get one online, pretty sure an officer of the law won't be particularly patient should I get pulled over or in an accident with an expired one...

It's perfectly legitimate to take your car to a mechanic and tell them "I'd like to take this on a long journey, please give it a thorough check and let me know if there's anything you would do before leaving."

Then I would do the normal preparations for being stranded - a case of water, a blanket, some jumper cables, a pump and a tire patch kit.