It is imperative that you have deadbolts installed on your home. While most regular knob and lever locks offer some degree of security, a deadbolt will deter or delay a break-in. However, one issue that occurs when a deadbolt is installed incorrectly is that the hole on the frame of the door, where the bolt goes when the door is locked, is often not drilled deep enough to allow the bolt to fully engage. If the bolt of a deadbolt lock isn't extended completely, the deadbolt is pretty ineffective as is any lock that is not properly installed.
Make sure to check your windows. If they slide open and are accessible from the outside, do you have a second form of lock on them other than the one that was provided with them? Most of the locks provided with the windows are only latches that simply hold a window closed, but don't really lock them. Most of them can be manipulated from the outside and opened with minimal effort.
Check your sliding glass doors. A traditional patio door is the most vulnerable entry point since it's usually in the back of the house, hidden from the watchful eyes of neighbors. These doors are usually only secured by the same type of latch that secures your windows, and many are installed incorrectly and can actually be lifted out of the frame from the outside even when locked. Just like your windows, make sure that you have a secondary form of lock on your sliding glass patio doors. Even a door pin, which helps to secure the movable door to the stationary door, and lessens the possibility of lifting the door out of it's frame.
If you have a gate that leads to the rear of your home, secure it with a lock other than what's typically provided. Depending on your brand of house locks, you can purchase locks for your gates that can be keyed up to the same key as your house locks so that you don't have to carry around more keys than necessary. Plenty of outdoor lighting is always a great idea as well.
Update your locks and add deadbolts. Locks are like anything else that you purchase in the sense that you get what you pay for. If you buy a $10 lock, well then you have a $10 lock. Why would you spend thousands of dollars for the stuff in our house and secure it with the cheapest lock you can find? One you have a good lock that's installed correctly, maintain it be keeping it lubricated and tightened to the door.
Keys and locks should be changed anytime you move into a new house, apartment or office regardless of when you are told it was rekeyed last; when you give out keys to people like contractors and repairmen or anyone that is not a regular key holder because you never know if they have had your key duplicated; when you lose a key; and just for safety purposes, once every couple of years.