Modern wells look just like csaws describes (
http://www.make-my-own-house.com/images/wellcasing.jpg). Older wells often are set into a pit and covered with a hatchway of some sort, or sometimes a round concrete lid. Your best bet is to locate where the well water inlet passes into the house, then examine your property on that side of the house. Should you locate a well located in a pit, you should be sure to never use it for drinking water, since pits are known for collecting surface water and allowing contaminants into the well.
If all else fails you can contact IDEM at (317)232-8603 and ask for the Drinking Water Branch. They
might be able to locate a record of your well through an address search.