a. Install security devices such as CCTV cameras, alarms, motion sensor, etc as this will help you track strange activities around you.
b. You can also employ trusted security personnel or bodyguard if the threat level justifies this, especially if you are a public figure.
These two shall come along together and you shouldn't only have CCTV for alarming you when strange activities are around your house. But also, there should be someone that has to be monitoring it for you. Because it will be useless if you have them and yet, you're not doing anything around it but just to watch when an actual thing happens by that time and no one is there to monitor but only your alarm.
There is a reason why CCTV cameras have staff behind it watching the monitors closely.