Change all the locks when you move into a new home. You don't know how many extra keys are floating around town. Instead of keeping a spare house key in the usual places, like under the doormat or in the mailbox, wrap the key in foil and place in a 35 mm canister and bury it where you can easily find it. Don't leave notes for workmen or family members. To keep your tools or items such as ladders, paint the handles of tools and parts of the ladder with bright colored paint.
Thieves tend to avoid stealing items that are easy to identify.
Fireplace logs can be hollowed out to make a hiding place fro small valuables. Hollow out the leg of a table or chair for hiding small objects. Drill from the bottom, then cap all the legs with rubber tips. Frost or cover your garage windows so burglars won't be able to tell if the car is gone. Install a peephole in the door separating the house and garage.