Your car's battery seems like such a small thing. However, it really is a big part of your car. Without your car's battery, your car isn't going to start. Before your car gets to the point where it doesn't start at all, you may often see some signs that the battery is starting to die.
1. Your car starts, but only sometimes: If your car starts just fine most of the time, but it occasionally won't start at all, that can be a sign that your battery has problems. It could be that your battery's connections have a problem. The first thing you should do is check them out. The connectors should be firmly on the terminal. If you can move the connector on the terminal at all, then it is too loose. It should be very tight on the terminal. Try tightening them up to see if that helps. Make sure that you don't touch both terminals at the same time. You would complete the circuit and you could get hurt.
2. Your car cranks and cranks before it starts in the cold: No one likes working in the cold. Your battery is no different. The closer to dying your battery is to dying, the less it wants to work in the cold. Cold will drain the power of the best and newest battery, let alone one that is old and wearing out. If your car doesn't want to start in the morning, but starts just fine later in the day when it's warm, then that can be a good sign that your battery is dying.
3. Your headlights are very dim: Your headlights draw power from your battery, especially when your car isn't on. If you aren't sure how good your battery is, you can always turn on the headlights and see how bright they are. Do this at night or in a darkened garage. It can be hard to tell if they are dim if you are checking them outside in the full daylight. If you can shine the light on a wall or the door, you can get a good idea of exactly how bright the lights are.
If you aren't sure what's going on with your car, you can always take it to a repair shop such as Import Specialty Auto. They will check out your car for you. That will include checking out your battery to see if it's holding a charge.