You car's air filter is very important since it maintains some parts of your car system clean and free of dirt. If your air filter doesn't work properly and dirt enters your car this might make it go through different problems, and therefore it is important that you check the filter and change it when necessary. Your mechanic can do it for you although it is very easy and you could do it yourself as well.
It is recommended that you change your car's air filter once a year or every 15.000 miles if you live in an averagely dusty area. But, if you can check it once in a while and replace it as soon as it needs it this would be much better. Checking it is a very easy thing to do and replace it is not complicated once you learn how to do it.
If you wish to check your car's air filter yourself and in an easy way, you can do so by using a light from inside pointing outside and check how bright it looks through it. If you see the light clearly, then your air filter is still good, but if you can't see much of the light then it indicates the filter needs to be changed.
Newer cars have different air filters than older ones. If your car is rather new, its air filter is probably rectangular and you might find it located under the hood, near the radiator area or the fender wells. In order to change it, you must open it and take the actual air filter from it, replacing it by the new and then closing it again.
If your car is older, then the air filter will probably be of a big round shape and located near the engine area. It might probably be screwed, and all you might need to do is to unscrew the cover, let the air filter come out, and place the new one instead of it. You must pay attention in case it has any other attachment mechanisms such as clips which you would need to take off as well.