Want to keep everyone off your property? You can try to accomplish this by filing an authority to arrest at your local police station and posting no-trespassing signs. Want to keep specific people off your property, like a spouse you are divorcing? You can get the equivalent of a legal "no trespassing" sign by obtaining a restraining order from the local court. Violation of either can send someone to jail.
TL;DR (Too Long; Didn't Read)
You can file an authority to arrest with the police that allows officers to arrest anyone found on the land. Or you can get a restraining order to keep specific people from trespassing on your property.
No-Trespassing Order to Keep Everyone Out
If you own a business and worry that people will trespass on your property when the store is closed, you can file an "authority to arrest" form with your local police precinct. This form gives police officers the right to arrest anyone caught trespassing on your property when the business is closed. An authority to arrest form must be completed and signed by the property owners or their legal agent. You have to return it to the police station in the area where the property is found. In order to keep this effective, you must renew it every year.
You also must post "no trespassing" signs that contain the proper language. They are mandatory to allow arrests to happen under the authority. Don't limit yourself to one. Place the signs at all entrances plus a few more around the property. Mount them at a height where they are visible to people walking by, but not so low that they can be removed easily. Check with your local law enforcement to find out your jurisdiction's signage requirements. Some states regulate the size as well as the language of the signs.
Restraining Behavior with a Restraining Order
A restraining order is a court order ordering someone to not do something, like entering your property or removing a child from the state. The courts typically issue these orders to prevent spousal abuse, stalking or other immediate harm.
A restraining order is always temporary. It is often called a temporary restraining order or TRO. Depending on the state, it may also be called an injunction, order of protection or something similar.
You ask for TRO at your local court. Many jurisdictions have online information about TROs, and many offer free downloadable forms. Alternatively, visit the court clerk’s office in person and pick up forms and instructions. When you complete the forms, you must provide details about what has occurred and why you need the order. Sometimes the judge questions before she signs the order.