Tires are literally between you and the road, and play an important role in the accelerating, braking, and corner of your car. Properly maintained tire pressure promotes longer life, increased traction and handling, and reduces the chances of a loss of pressure that strands you at the roadside.
You need a common tire pressure gauge, and a source of compressed air. There are many types of gauge, but they all essentially work the same way and fit a standardized tire valve stem. Compressed air is commonly supplied (sometimes at a cost) at gas stations, service centers, and car dealerships.
Tires heat up from friction with the road surface, increasing tire pressure. If you can't let them sit overnight, allow the tires to cool for three to four hours out of direct sunlight.
It's a good idea to keep a few valve stem cap spares in the glove box; they have a way of getting lost.
Some businesses may provide compressed air for free. You may have to ask an employee for the compressor's fitting if it's not permanently attached.
It's easy to overinflate a tire, but it's also easily remedied.
Most tire pressure gauges have a small dot or bead on the backside that is designed to be pressed into the center of the valve stem, releasing air.
As you dial in the correct pressure, add or release smaller and smaller amounts of air.