If I thought that there was something illegal going on at my neighbor's house, I would call the police, especially if I thought it had something to do with drug dealing or anything else that could bring with it a violence component. And while I would try to make sure that I had something more concrete than just an idle suspicion, in this type of scenario I would rather be safe than sorry. I would rather ruin a potential relationship with my neighbors than perpetuate any illegal dealings near my home.

I would call the cops and have them investigate. You can call the non-emergency number, give them the address and leave an anonymous tip that there is something strange going on at that house and you are worried it may be illegal. They'll send some people out to look into it and hopefully it will be ok and you then you can get back to feeling safe enough to mind your own business. If you don't feel safe and are trying to figure out why, you shouldn't be minding your own business. You should do what you can to protect yourself.

Call the cops every time you feel unsafe and ask for a patrol. Do not call 911 unless there is a clear and present emergency. If all you need is a patrol, call the non-emergency number. If nothing else, increasing police patrols will help deter illegal activity. Remember, though, that by calling the non-emergency number, you may not see an immediate response. It may take a few hours, but as long as there's nothing clearly dangerous going on it should be OK to wait it out.

The cops may find something and do what they need to do to stop it OR they may find nothing, but you need to protect yourself if you suspect drug trafficking or anything illegal.

I would mind my own business. I live in a small enough town that if the two police stations, that we voted against don't have enough officers, that we voted against to catch a large drug operation then hell, my neighbors deserve to get away with it. Plus I don't think what my neighbors do is any of my business. I wouldn't want my neighbors calling the cops on me because they suspected I may be selling drugs. (and I could see how they could, I have cars come and go regularly and stay up all night) You never know how big of an ass your assumptions can make you, until you make them.

The only exclusion to this answer would be I had actually SEEN hard drugs and the traffic they were attracting was putting my family and belongings in danger.

I DO have drug dealing neighbors and I ignore them. If I get annoyed by them I will call the police. If they keep it low key, I will continue to ignore them. If I think they are talking to my kids (teens) then I will take a more direct approach and let my inner redneck come out.

If I thought the suspicious activity was going to negatively affect me, I would definitely report it. I normally try to more or less mind my own business, but it's really important to me that my good neighborhood remains a good neighborhood. However, doing some investigation on your own first doesn't usually hurt.

Don't do anything, even if you know what it is. You haven't been brought into this, and you should leave it that way. Take care of your own doorstep.