If you regularly have to jump start your car or if it has been starting slowly, it may be time to consider replacing your car's battery. Before changing a car battery there are a few steps to take to ensure that it is the cause of the issue. If your car has a voltage gauge a fully charged battery should read around 12.6V with the engine off. If the voltage is low the battery may need to be charged or replaced. The gauge should be above 13.5V with the engine running, otherwise the alternator or charging system may not be functioning correctly. If your car doesn't have a voltage gauge you can use a multimeter or have a shop run the tests for you.
Car batteries are categorized into different groups based on their size and shape. It is important to use a battery from the proper group so that it will fit your car correctly. Batteries also come in different capacities, measured in amp-hours. Normally you should change a car battery with one of the same capacity, however there is usually no harm in using one with increased capacity.
If you have a battery saver, connect it at this point to save your radio presets and other settings following the instructions provided with the device. If you do not have a battery saver make sure that you have any PIN numbers required for the radio or other equipment in your car.