Did your landlord lock you out? You should first ask your landlord to let you back in.
If that does not work, notify the police department that serves your town that the landlord has committed an illegal action. The police can contact the landlord and advise him that he must let you back into your home. The protocol that police should follow on this is set out in Police Bulletin 93-1.
If the landlord refuses to let the tenant back in, the tenant may use reasonable force to get in, such as cutting a padlock or forcing open a door or window.
Caution: If a landlord has gone to court and obtained a court order called a "Writ of Possession," the landlord has the legal right to change the locks after you have been served the Writ by a Sheriff.
If the landlord refuses to let you back in and the police have not been able to help, you should talk to a lawyer.