You have to do a lot more than gather supplies to make your car road trip ready. With the following advice, your car will be more than ready to hit the road:
Get A Once-Over By Your Mechanic - Take your car in to a reputable car maintenance place in order to get it looked at before your trip. Ask him to look out for anything that would be a cause for worry if you were taking the car on a road trip. Mostly, fluid checks and other standard maintenance will go along with it. Have him look at the tires for the amount of wear, and be sure to change the oil and filters as soon as you can, especially if you are close to the 3,000 mile mark.
If your trip will be during the summer months, have the air conditioning system inspected to make sure there won't be any mid-trip surprises. If your vehicle has four-wheel drive or any other special features, have the mechanic inspect the system to be confident it will function properly while on the road.
Gather a kit for emergencies - pick a place to put an emergency kit in the car, so you have it if something were to go wrong. It must have flares, first aid kits, hazard cones or flags, and things like that. If you have these things on hand, you will be prepared for anything.
Stock your toolbox - Keep a took box handy, which includes socket wrenches, jumper cables, tire irons and whatever else you think you might need if your car runs into trouble when you are on the road.
Spare Tire - Be sure that you have a proper spare tire that is inflated adequately, as you will always have to worry about hazards on the road that can lead to a flat tire. Having this extra step will help you immensely if things go wrong.
Keep the Car Clean - Road trips can leave a car cluttered and messy. If you clean it out properly before the trip, you will have a much better time and not have to worry about a bigger mess later.