The neighbors around your rental property are your allies.
Second is to knock on their door. They will also probably be happy to talk with you at their door.
Either way, get their phone number as well. If you suspect that your tenants are not behaving the way you would prefer, call them to get their impressions. One of three things will happen. One, they won’t have noticed anything and will tell you so; two, they will have noticed something and tell you about it; or three, they will have noticed something, won’t tell you about it, but, since they are friends of the offending tenant, will tell him or her. Them telling the offending tenants that you were asking about them may be all that is needed to get them to clean up their act.
If the neighbors are having problems with the tenants, here is what to do.
1. Tell them you want to correct the problem, but need their help to stop the behavior and/or get the tenant out.
2. Ask them to document the instances noting time and date. Assure them that you will not tell the tenant where the information came from. Chances are you will get similar information from several neighbors, anyway.
3. Call them back or stop by their home in a week to collect the information.
At that point you serve notice on the property that the tenant has 14 days to correct the violation of the rental agreement or move out in 30 days (or however it is done in your state). That is called a “30-day-with-cause” notice. It is important that you itemize exactly how and when the tenant has violated the rental agreement. The more specific you are, the better the effect on the tenant. If you have a problem drafting the letter properly, call your attorney. But get the evidence first.
If they do not correct the problem and do not move, you begin eviction proceedings.