You should also have an electric fan that will kick on when it needs to, but it wont run at the same time all the time. I would check your thermostat first..Its the cheapest easist place to start (if you arent leaking antifreeze or are low on antifreeze that is).. If you are mechanically inclined, take it out and you can test it by putting it in water and slowing heating it up. When it reaches 180* F it should pop open, if it doesnt that is your problem. If its fine, could be something else like the water pump, or a problem with your radiator....If you are not mechanical, take it to a shop and have it checked out.
The things you can do yourself is just check you fluid level and make sure you have enough, and then watch for leaks. Other than that, I would take it in..