Car check list before a long trip

Other items to check under the hood

Under the hood

Check the brake fluid level. Low brake fluid level may indicate worn out brake pads - have your brakes checked.
Check the power steering fluid.
Top up the windshield washer fluid. You can find the correct procedure in your owner's manual.
Look for anything irregular - leaks, loose clamps, kinked hoses, etc.

Lights and other electrical equipment

Check the lights

Check the horn, wipers and all the lights. A couple of spare bulbs (one for the headlight, one for the back) might be useful. Make sure your heater / air conditioner works properly. If you haven't changed the cabin air filter (pollen filter) for a long time, consider replacing it. When it's dirty, it restricts the air flow for the air conditioner or the heater. Have a broken or cracked rear view mirror? Fix it before the trip.

Windshield wipers

Changing wiper refills

Replace the wipers if they don't clean the windshield properly. If you still have the original wipers installed, you can just replace the rubber refills; they cost just a few bucks and can be purchased from your local dealership's parts department. Check if the windshield washer jets are working properly. If the roads are wet or slushy, it's good idea to take an extra windshield washer fluid with you.

Tires

Measuring tire pressure

Check the tire pressure. Recommended pressure is indicated on the manufacturer's label, which usually located in the driver's door frame or in the glove box. You also can find it in the owner's manual.
If you feel a vibration at highway speed, have your tires balanced. There is a safe limit of the tread wear. If the tire is worn below this limit, it's unsafe to drive. Uneven tire wear indicates alignment problem.

Brakes, steering, suspension and drivetrain components

I recommend to have your car inspected in a garage before the trip because many components of the brakes, steering, suspension and the drive train can only be properly inspected in a repair shop when the car is on the lift.
Here are just a few signs of possible problems:
Feeling any vibration in the steering and the pulsation in the brake pedal while braking - have your brakes checked for possible warped rotors.
A clicking or popping noise when turning could be an indications of a bad or worn CV joint.
Having a knocking or rattling noise coming from the suspension while driving over bumps? One of the suspension components is probably loose. Have it checked, it might be unsafe to drive.
Look inside the wheel arches - do all four struts (shock absorbers) appear dry? A leaking strut or shock absorber should be replaced before a trip. Once the shock absorber will lose enough oil, the car will start bouncing like a boat and any road roughness can throw the car out of the road.
Does the car feel unstable and wander from side to side at highway speed? Is the steering wheel out of center? Does the car pull aside while driving straight? Have the wheel alignment checked. Improper wheel alignment can cause handling problems, increased tire wear and it's very uncomfortable to drive when the car constantly pulls to one side.

Spare tire, wheel wrench and the jack

Spare tire and the jack

Check the spare tire pressure. If it's a full-size (the same size as the others tires) spare, the pressure should be the same as in the other tires. If it's a small temporary-use tire, the proper pressure is indicated on the sidewall of the tire (usually 50-60 psi). Check the owner's manual for the exact data. If your car has a spare tire that is secured underneath, make sure it can be easily removed; the mechanism could be rusted. Check if the jack is still operable.

Wheel lock key

Spare tire and the jack

If you have wheel locks installed, make sure you have the key and the wrench to open the wheel nuts.

Basic emergency kit for your car

Emergency car kit

A basic emergency kit for your car can include:
- Jumper wires
- Tire sealer-inflator can
- Tire gauge
- Couple of rags and work gloves
- Flashlight
- Basic tool kit with screwdrivers, pliers and set of most common sockets.
Consider also a spare headlight bulb and a couple of fuses, bottles of engine oil, windshield washer fluid and coolant, an emergency stop sign or flares, an electrical tape, spare ignition key, etc.
Don't forget your personal emergency kit with First Aid kit and items like a blanket, a bottle of water, couple of energy bars, etc.

Consider GPS Navigation System

GPS unit

If you like long car journeys, this small piece of equipment can save you a lot of hassle. I travel by car a lot and time and time again I was thankful for having this small device. Not only it can show you the route and estimate your arrival time, it also can direct you to the nearest gas station, coffee shop, park or many other points of interest.