[Madhatter]

wooden frames get drilled and a screwdriver pushed in or fish wire used to lift or pull side handles, esp the old ones with the spiral on, and to lift the bottom stay, always usee window locks and use them. Single glazed windows can be cut with a cicrcle glass cutter, very james bond but easy to do. Double glazed windows used to be fitted from outside at one time, but now tend to fitted from inside. If I can get the glass out from outside so can a burglar, You should think about getting them bonded in or replaced with ones fitted from inside. Pvc windows are hard to lever open with a screw driver, wooden are a lot easier, esp if no one is near to hear. Back doors are often wooden, with a single mortice lock, best thing to do is replace it with a multi point locking pvc with no glazing, if not make sure its not got a thin panel in the bottom thats often only held in with panel pins, these are a council houses norm. Also fit a five lever mortice, councils only fit three and only tend to have 999 different keys. I know of two flats that have the same key, the locks fitted 12 months apart. also fit a surface dead lock, about 60 quid, make sure its a good one that you can't push the latch back with a credit card once its been closed, it should have a thin second latch as well as the main, once the door is closed that bits gets pushed in by the door frame and stops the main bolt being puched in with a credit card, you should also be able to lock it with a key when you go out rather than just pulling closed, a stick can be pushed through the letter box or even an arm and the lever pushed up. Don't just rely on the surface latch though no matter how good or expensive fit the mortice too, the cylinder on a surface latch which most people call a yale is easy to extract with the right tools. as said above never leave a key in the door on a string by the door hidden outside, they know all the places to look, use fish rods wires, or even get their hand through letter boxes. You could also fit hinge bolts and rack bolts, door viewer and door chain.
Think, if you lost your keys, how would you get in.
Usual other stuff you should do, security lighting, dusk to dawn sensor or a pir to switch it on when someone aproaches. A good burglar alarm with auto dialler to call you if it goes off. gravel is good for paths, it's noisey to walk on, thorn pushes by fences and trellis on top of fences can be good, they want a nice easy escape root with the goods.
CCTV can be fitted, but needs good light at night esp if its coloured, a bw camera or day/night camera that changes to bw at night or low light level camera is best.
You should not have a cctv camera monitoring public places, theres a whole list of laws and regulations that you'd have to comply with.
Don't leave car keys on the rack down stairs at night or if you go out, people break in just for car keys nowdays.