The ideal security for a (wooden) front door is an automatic deadlocking rim lock, one third from the top of your front door, together with a mortice deadlock to British Standard 3621, or the equivalent European Standard EN12209 one third from the bottom (always avoiding construction joints).
Back doors should be fitted with a five-lever, two-bolt mortice sash lock.
Remember that quality locks are only as strong as the door and frames they are attached to, so consider replacing worn or flimsy doors.
If you live in a property with a communal entry, fire regulations need to take precedence, so consult a fire officer as well as a crime prevention officer.
Whether you have glazing on front, back or French doors, consider replacing ordinary glass with laminated glass, "an effective deterrent to all but the most determined burglar", according to the Glass and Glazing Federation, 0171 403 7177, which can advise on ways to improve overall window security. The Laminated Glass Information Centre, 0171 499 1720, will advise on the types and best use of laminated glass.
Shed owners should consider the use of a strong, lockable box or cage to store garden tools which can otherwise equip a burglar with all he needs to gain easier access to the house.
If you are short of cash for major security upgrades, plant thorny, unfriendly plants around your perimeter fences and under windows. A brush with, say, pyracantha firethorn (aptly named) would give most burglars pause for thought.