My ex's mother had to go stay with his sister after an emotional breakdown due to her divorce. He was mainly in charge of taking care of her house, even though we lived an hour away and his irresponsible brother lived five minutes away. He would always make sure the plants were watered/kept neat and removed any mail or promotional flyers to ensure the house did not appear unoccupied.

He discovered that people would put things like a glass beer bottle in front of the house, I guess to test to see if someone noticed it, and removed it. He always got rid of those and also asked the neighbors to help out if someone noticed it.

Here, there is also a problem with potential thieves or burglars scoping out neighborhoods and putting spray paint marks on the sidewalk or front fence/gate. They are some sort of code, to indicate things such as that the household is on vacation, elderly people (seen as easier to rob) live there, the household has a dog, or a police officer lives there, etc. We have a regular police service and the investigative police (like the FBI) and they both have more leeway to use their guns than an average citizen, so criminals like to avoid those houses.