When your neighbors have people coming and going to their houses all hours of the night, it could be indicative of something unsavory. Bad things could easily be going on during the night when the neighborhood is asleep. Your neighbors could be dealing drugs, running a meth lab or even harboring criminals.

Perhaps your next door neighbor is very old, rarely comes outside and never has visitors or any visible activity. Though this neighbor may not appear dangerous, his or her carelessness in leaving on the gas, a stove or a faucet could result in danger for the neighborhood.

A very neglected house can be an indication of dangerous neighbors. Newspapers left outside, messy lawns and old cars in the driveway could be signs that neighbors are up to no good. The noise level may be very high at inappropriate times. This not only is annoying but also could be an indication of a hidden agenda. The people inside could be abusing each other, having drug parties or hiding from the law.

Both kids' and pets' appearance and activities are a good barometer of what is going on inside the house. A pet left outside all the time that looks neglected and malnourished and growls a lot could be a sign of dangerous neighbors. If the kids are never outside or run away when you offer a greeting, this behavior could be an indication of child neglect and endangerment.

Seeing the police often at a neighbor's house could be a red flag that your neighbors are dangerous. Abuse among parents, children and animals is possible. If you are not sure why the police are called, check with other neighbors or the police department. Concerned neighbors should start a neighborhood watch when they suspect any danger. If there have been burglaries, noise and neglect, look into it. If you suspect someone of being a sex offender, check the sex offender registry.