If your tire pops on the road, don't panic. Pull over safely and slowly to the side of the road where there is a flat surface, put the car in park, and set the emergency brake. Get out on the side away from traffic.
Grab your tools. You will need the jack, the tire, the tire iron, something to hold the nuts in, a tire pressure gauge, and possibly spray-on lubricant. Usually most of these are stored in the trunk of the car or under the back of the passenger seat. The tire could be in the trunk or under the car. If you check your tire pressure regularly, your tire pressure gauge might be in the glove compartment or another convenient location.
Check the spare tire's air pressure for good measure. All tires lose air over time, and harsh weather conditions such as cold can drain air from a tire also. There isn't much you can do if the tire is flat or low on air, but a well informed driver is always a good thing. Regular car maintenance requires that the spare tire's pressure is checked when the other tires are checked and replaced.
Halfway loosen the nuts holding the tire on. They might be a little tough to get going at first as the nuts haven't moved in awhile and debris can easily clog the threads. This is why you want to loosen them before you take the tire off the ground. A little spray lubricant should help get them going.
Put the jack under the car and line it up with the jack point. These points can be different for each car, so look it up in your owner’s manual if you are not sure where it is. Raise the jack slowly so you do not damage the car just in case you make a mistake.
Loosen the nuts the rest of the way and put them in a safe place. Although tire nuts are not very small, they can be difficult to find in grass or can easily roll away on the road. A plastic bag or bowl is ideal places to keep the nuts until you need to screw them back on.
Take off the flat tire and replace it with the spare. Slide the nuts back on and screw them snugly back into place. Spray them with lubricant to make them easier to remove next time. Release the jack, put all of your tools back, and store the old tire in the trunk for recycling later.
When pulling out and back onto the road, maneuver slowly at first to make sure the tire is on properly.