What else needs to be registered so I can use my drone?

I will readily admit that I have not kept up with legislative changes as they relate to drones. However, your line of questioning tends to suggest that "regular" laws related to privacy would be in play. If you're trying to see how low you can get your drone over private property, or how close you can get the drone to other people, then you're playing a dangerous game with invasion of privacy laws, nuisance torts, and a variety of other potential legal violations or causes of civil action. Many legal analysts have even suggested that drones can be legally shot down by private citizens under certain circumstances, so you are risking a lot when you send your drone to property that you don't have a legal right to be on. Unless you have a commercial activity that requires you to fly a drone over someone else's property (at which point I believe you require a license or waiver from the FAA), I would not suggest trying to push the legal limits by sending your drone onto someone else's property or in their personal space.