Don't make it easy!
It only takes a minute to remove temptation from the sight of would-be theives and this is espcially important if your room is clearly visible from the street. Always take the time to close and lock windows and doors when you leave your room and hide any items of value such as cash, laptops, keys and mobiles so they aren't on display for passing eyes.
This goes for your car too, do not leave anything on display even for a short time and always lock your car even if you are just popping to the shop.
We realise that you will be bringing back a whole heap of stuff when you arrive at uni but don't be tempted to leave it in the car whilst you show your family your new home and especially not overnight!