These 10 faults are, in order, the most common problems dealt with by AA patrols. More than four out of five rescues could have been avoided through pre-journey checks and regular maintenance. AA patrols can fix many of these faults at the roadside, but most would never have happened with the correct preventative care. 

Lead/acid batteries have a life of around five years. The most common problems are with terminals and clamp connections, and loss of voltage caused by constant use on short journeys without regular recharging. At every service, check that terminals have been cleaned and protected from corrosion by a layer of petroleum jelly or grease. Clamps must be secure. A fortnightly overnight charge prolongs battery life if you seldom make long journeys. Modern maintenance-free batteries need no top-up.

Check tyre pressures at least fortnightly. Know the correct figures for different speeds and loads, and adjust pressures accordingly. Kerb impact can damage sidewalls and, possibly, wheel rims - both can result in slow leaks. Consult an expert tyre dealer if any damage is visible. 
When checking tread depth, look carefully over each tyre: wheel misalignment could be the cause of uneven tyre wear. Remember to include the spare tyre in your checks - a worn or flat spare will be of little use in an emergency. Check that your jack and wheel removal tools are in good condition.

Keep a note of the identity number of the keys supplied with the car when new - it speeds up replacement. 
You must provide some proof of ownership if you call out the AA to unlock your car.
Always carry a spare set of keys with you.

Many modern cars come with sophisticated immobilising systems and alarms. These certainly protect against theft but they can be a headache, literally, when they go wrong. 
Whether it is a blaring alarm keeping the neighbours awake, or an immobiliser that refuses to recognise its owner, AA patrols invariably get the problem sorted out on the spot.

Persistent battery problems can indicate alternator/generator faults, as can dim headlights when the engine is idling. 
Belts driving the alternator may also operate the radiator fan and water pump - a rapid rise in engine temperature could indicate a broken belt.

Though starter motors are usually robust, they can fail through wear of the gear engagement mechanism in the motor (or on the flywheel). Spring weakening and corrosion or sticking of the gear on its sliding shaft are other problems. 
The solenoid operating switch may fail or the terminals may corrode. Good regular maintenance should highlight potential faults.

Empty fuel tanks cost AA patrols a lot of time. But there are other fuel faults, such as broken pumps, leaking pipes and blocked carburettor jets. Injectors, both diesel and petrol, can simply fail. 
AA patrols carry (and charge for) spare fuel and can make some temporary pipe and carburettor jet repairs, but very often parts have to be replaced in a workshop.

Even minor accidents can be major headaches. The AA regularly recovers damaged vehicles on its members' behalf. These cases need garage and body shop repairs to be roadworthy again. A call to the AA takes the hassle out of organising help to pull the damaged car out of busy road locations and deliver it to the repairers.

The clutch cable is a component under high stress. Abrasion can shred the wires in the cable until it breaks. Temporary repairs can often be made, but the best solution is a workshop replacement of the whole cable.

The spark plug is a much neglected and abused component of the ignition system. 
Make sure that you replace plugs at the manufacturer's recommended service intervals - usually every 10,000 miles (16,090km).