You cannot do what is called "self help evictions" where you do things like change the locks, turn off power, or otherwise impede the residents access to the property, even if they stopped paying rent. You must get a court ordered evicting them.
You need to hire a lawyer familiar with evictions. I've found that apartment complex managers usually know a few good ones that they've used in the past. I'd recommend stopping by a apartment complex and talking to the leasing manager and asking who they recommend.
As a disclaimer, I am not a lawyer, and this is not legal advice, you should always consult an attorney regarding legal issues :)
We are still trying to get the home cleaned and repaired for a new tenant.
Be careful. My tenant took down the light fixtures, and punched holes in the walls, broke windows.. etc., then called Code Enforcement. You may find that they leave your property totally trashed and most likely they will not move out without a fight. Property managers are experienced with these situations.