If you take it to an official oil change place they always put a sticker on your windshield saying to change the oil every 3,000 miles or every 6 months. This for the most part is total BS. They just want you coming as much as possible.
I suppose if you had an old model car with a carburetor this is could be true but for most new modern cars that have a fuel injection systems, 6 months is really too early to change it (you are just wasting your money and perfectly good oil). Of course, the most accurate information comes from your owners manual.
I know that for my Honda, the owner manual says every 6 months under if you drive under severe conditions (i.e. towing a trailer, a large roof rack, driving up high elevations mountains in Alaska or the arctic circle). For most people, just go by the normal schedule in the owner's manual which for my car anyway is every 5k miles or every 1 year whichever occurs sooner. I have done this and my car has been working fine for about 13 years now with no problems.