Immediately
Consider changing the locks as soon as you move in - you never know who has a spare key. Then take a good look around to ensure that security is up to scratch. The British Crime Survey suggests that installing even the most common home security devices greatly reduces your chance of being burgled - and you'll have greater peace of mind. See Feels Like Home for more on settling into your new property.

Added bonus
Many insurance companies will give you a discount if you follow their approved security guidelines. Most of these devices are available in DIY stores and are easy to install. But check carefully with your insurer about their specific requirements and confirm whether certain features need to be professionally fitted to qualify for a discount. See Get Insured.

Doors
1. An outside door should have a five-lever mortice deadlock fitted about a third of the way up.
2. Be extra safe and fit a bolt, as well as securing the door hinges with hinge bolts - these are inexpensive but can help protect your door against a forced entry. But these are only as strong as the doorframe itself, so reinforce it with a steel strip or replace as necessary. Ideally doors should be made of solid core construction at least 44mm (1.7in) thick.
3. Glass panels near the lock give burglars easy access. Replace them, or at least make sure they're laminated glass.
4. Fit security locks at the top and bottom of patio doors to stop the frame from being lifted off its tracks.
5. If you're in a flat, the front door tends to be the most vulnerable spot. Talk to your neighbours about having a telephone or video entry system installed.
6. Consider an automatic deadlock that when locked from the outside with a key cannot be opened from the inside - so if a thief enters through a window they can't exit through the door. But be careful of fire regulations and exit access, as these must take priority.
See the step-by-step guides Fitting a Door Lock and Adding Security Bolts To a Door for help when installing door locks.

Windows
1. Most burglars enter a home through the windows, so take extra care. Fit key-operated locks on all accessible windows. Pay close attention to windows on the ground floor and near drainpipes and flat roofs. These locks are inexpensive and easy to fit. See Fitting a Window Lock for more help with this.
2. Even small windows and skylights need locks - an agile thief can get through a gap no larger than a human head.
3. Never leave the key in the lock - this is an open invitation.
4. Additional security can be had through fitting security grilles to exposed windows - DIY shops sell different designs.