Find a reason to go. Look up your destination city and find concerts or events that interest you. Set your date around those events. Look up good places to eat, too. Read all reviews. It saves headaches and Pepto Bismol.
Map out your route and decide how many overnight stops you will need, then book a hotel on Groupon.com
Go online and get AAA for $50. It's cheaper and faster than waiting on Ray Bob's towing at 2 AM on I-5.
Go to Jiffy Lube or somewhere for an oil change and have them check your fluid levels and belts if you don't know how to do it yourself. Tell them you're going on a road trip and ask if the car is up for it. They make try to convince you to get a service that day that you'll need in the future. Just tell them it's a family emergency and you don't have the time or the money.
Get a spare tire. You can get a cheap used tire at any tire shop. zOr check the one you have and make sure it's not flat. Check your tire pressure on all your other tires too. Make sure you have a jack and wrench.
Buy your own jumper cables. It's easier to find someone with a car who is willing to give you a jump if you already have cables. A lot of people will help but don't have cables.
Load up at the 99 cent store: water, snacks, personal hygiene/feminine hygiene products, paper towels, water, first aid supplies, cheap games in case you have time to kill. Get disinfectant wipes too. You'll be using some dirty restrooms.
Get cash money and keep large and small bills separate, ideally in separate pockets in your pants or purse and jacket. Don't pull out a wad of cash to pay for a burger. People will be watching you.
Put aside money for your return trip. Don't get on the road back home and find out you spent all your gas money.
Share your itinerary with someone before you leave. Text them every morning and evening to let them know your night/day was ok and that you made it to your next stop.
Carry a weapon. Yep. I said it. A bat, tire iron, pepper spray, etc. Keep it in the car within reach, not in the trunk.
When you get to your destination, turn on your GPS and open the Groupon app. It will show you all kinds of things to do in that area.