Sometimes its best to leave things to the professionals, but there are actually quite a few car repairs that anyone can do. Even if you don't know anything about cars, you should be able to do these simple car repairs yourself.
Possibly the easiest thing you can do for your car is change the air filter. On most car models, the air filter sits right on top of the engine and is contained in a black plastic box. You'll just need to unclip some metal hinges or remove a nut to pop off the cover. Inspect the old filter and compare it to the new one to see if you really need to replace it. If it's fairly dirty, go ahead and swap in the new air filter. Remember to close the cover and make sure it seals.