Maintain actual possession of the real estate at issue for the legally required period of time. You need to have a physical presence on the property, not merely some sort of verbal claim. For example, you need to maintain items or structures on the premises. In the alternative, you need to regularly enter onto the property. In most states, actual possession of the property must be for a period of at least 15 years.
Use the property in an open and notorious manner. You need to be public in the manner in which you use the property. You cannot be clandestine or "sneak about" on the property. Consider placing a no trespassing sign on the property.
Establish exclusive use of the real estate. Your use of the property needs to exclude other individuals in order to establish squatter's rights. In other words, you need to treat the property as your own and keep other people off the real estate as if you are a true and legal owner.
Use the property in a manner that is counter to the interests of the individual or business who has technical legal title to the property. You cannot appear to be using the property as an agent or in conjunction with the title holder of the premises.
Make use of the property in a continuous and uninterrupted fashion. There can be no interruption in your use of the real estate whatsoever if you desire to establish squatter's rights. If you stop using the property even for a very short period of time the 15-year clock resets to the beginning. The time needed to establish squatter's rights starts running again from day one.