If you have an address a local Realtor can check it out for you. Also, you can check with the county records to contact the owner. Then there is the direct contact with the occupant (could be dangerous). By the way is there a sign on the property?
Elizabeth you had some good replies, but to add to mine,,,, sometimes the owner request that there be no sign........ cause they don't want the neighbors to find out real soon, it might prompt them to sell and add more competition.... just a thought.
If you are a buyer, the direct approach may work. Knock at the door!! If someone answers, ask if they own the property. If they do, ask. If they are renters, ask anyway. If the property is vacant, then check the other options, or ask a realtor to assist you.
Most communities have websites these days that allow you to check property ownership records. If the property address and mailing address are identical, you have a good chance that the owner resides at the property that you are interested. If there's no for sale sign at the property, knock on the door and ask if the owner might be interested in selling. I would, however, first do some research regarding the value of the property to see if it's in your price range. A local real estate agent can help you with that. Good luck.
Why do you think it might be for sale? You can ck ownership records through the tax assessor or county clerks office. This will provide you recent history of any title transfers. You can write to the property owner at the address reflected on the tax bill.