You could always go there one day (or a few days to be sure) and just chill in your car or on your bike or skateboard, watch the place and note any activity/patrols and note the times of any activities
When you go, I suggest Pre-Dawn definitely
Keep an eye out for cameras and sensors on your way in and while inside.
If you suspect you tripped a sensor or walked by a camera you have 3 options
1 - Go Home
2 - Roll the Dice
3 - Leave, sit in your car or be somewhere that you can watch the main entry and wait for a response.
If you go with option 3, which you should, and there is no response you can now go inside knowing the cameras and sensors are likely just there for show or a part of the old security system.
When inside the property watch for a patrol, usually hourly..when they walk/drive by you have lots of time to make your way in until they come back.
When inside, walk quietly, peek around corners/listen before making a move into a hallway or around a corner
Wear your rubber boots!
This is all pretty basic stuff that most on here know, but if you don't...well now you do
Oh, and keep a spare memory chip in your pocket to swap out discreetly if you get caught!
The End