Go and leave your business card, tell them something about yourself and your family, what you do, what you can help with, ask what they do, welcome them to the neighborhood etc.
Once you talk to them several times you can occasionally mention; oh by the way, I wanted to ask you something...and take it from there...
Everybody wants to be welcomed into the community...
Some blocks do parties to greet their neighbors...
Once you have established a friendly base, mention the issue then,
and offer the solution that is a win/win.
Hope this helps,
Beachfront Realty, Inc.
You can also introduce yourself to your other neighbors and get to know them as well. They may be able to offer you some insight into your other neighbor.
Once you have a better understanding, then you should be able to come to a possible solution on how to address the property. If they are renters you could find the owner and address the issue with the owner. If they are hoarders or the property is in disrepair the city may have an ordinance and you may need to call them.
Come from interest in them first, come from contribution and solution.
Have an amazing day!