A car that won't start usually points to one thing: a dead battery. A battery can have a few things wrong with it that won't allow it to keep a charge including: a dead battery, a bad electrical connection, or low water in the battery cells. Charging a dead battery can be done easily with another car and jump leads or by using a 12-volt DC battery charger.
Get inside your car and under the steering wheel on the left side there should be a handle to pop your hood open. Pull the bonnet open handle and keep your hood open; use the propping mechanism provided, if the hood doesn't stay open on its own. Drive another car up in front of or beside your car (so the bonnets are near each other). Then keep the non-dead car running and pop open the bonnet on the vehicle.
Connect the jump leads to the running vehicle first. Do not let the jump lead black and red connectors touch because it will cause sparks. Connect the red clamp to the positive terminal and the black clamp to the negative terminal. Then connect the other end of the jump leads to the dead battery the same way.
Let the battery charge for about a minute. Try starting the vehicle which had the dead battery. If it starts, then disconnect the jump leads from both vehicles and let your car run for a while the alternator charges the battery.
Get inside your car and under the steering wheel on the left side there should be a handle to pop your hood open. Pull the bonnet open handle and keep your hood open; use the propping mechanism provided, if the hood doesn't stay open on its own.
Use a flathead screwdriver to pry the two lids off the cells on the top of the battery. Avoid spilling any water in the cells. If the cells are dry then the battery can't hold a charge. Buy distilled water and fill them about a half an inch from the top and replace the cell lids and tap them back on.
Remove the battery cables from both the positive and negative posts on the battery with a wrench or pliers. Use a wire brush to clean both posts of the terminal and clean the inside hole of the battery cables. Mix a couple of teaspoons of baking soda into a cup of water and slowly pour the mixture on both the battery posts and the battery cable connectors.
Reconnect the battery cables to the battery. Plug a 12-volt AC car battery charger into a standard 110-volt outlet to charge your battery and remember to connect the red clamp to the positive terminal and the black clamp to the negative terminal. For best results, use a boost charge for a few minutes, then slowly charge the battery until the meter shows it is charged. Once the battery is charged, remove the charger clamps from the battery and shut the hood.
Remember to read the charger's manual and use safety precautions before operating.
Practice safety with the jump leads and don't let the black and red connectors touch.