Step 1: Check price comparison sites
To be sure of finding the very cheapest headline price, check at least one of the main price comparison websites which compare the prices on offer from dozens of car hire brokers and smaller companies. You don’t book direct with the site but link through to the company offering the deals you are interested in. My top three to try first would be:
Step 2: Check the brokers
Brokers negotiate the best prices they can with different suppliers in different destinations. So you might end up booking with holidayautos, but when you pick up the car it will be supplied by, for example, Avis. In most cases the price you pay the broker will be lower than booking direct with the company that supplies the car, but you can never be absolutely sure of this.
Step 3: Don’t rely on airline links
If you're booking a flight, don't assume the "special deal" on car hire by the airline's site is necessarily the cheapest. While Ryanair has an agreement with Hertz and both British Airways and Flybe work with Avis, there's no guarantee that this will make car hire cheaper - and they can be more expensive than booking direct with a broker.
Step 4: Compare like with like
Quotes are usually based on a type of car or are banded 'economy', 'family', '4x4', 'people carrier'. While this can make it seem difficult to compare prices for specific models, companies do tend to use similar terms. However, there may be key differences which affect the price of a similar size of car - such as whether it has air-conditioning, the size of the engine, manual or automatic gear box, etc.
Step 5: Check what’s included
Once you’ve found the right car at what you think is the right price, double-check what's included. Collision Damage Waiver (CDW) and Theft Waiver (TW) usually are, and you shouldn't pay extra for Personal Insurance (PI) and Personal Effects Cover (PEC) if they are included on your travel insurance policy (they usually are). Local government and airport taxes can bump up the bill, especially in the US Super Collision Damage Waiver (SCDW) to reduce liability for excess and to cover damage to windscreen, roofs and tyres (areas that are not usually covered by CDW) will be an added extra, which can make a big difference to the final price - and may be payable on arrival at the pick-up desk. Be absolutely sure you know how much you will be charged for this - and consider taking out a separate policy (see step six) to cover them instead.
Step 6: Shop around for extra cover
It is usually cheaper to pay for extra insurance cover through a specialist insurer rather than through the company through which you are hiring the car - whether this is to cover the "excess" amount you would have to pay after an accident or damage, or to upgrade liability and CDW insurance in the USA.
Note that there are some restrictions and exclusions attached to these policies - for example, the validity of the cover in the UK may depend on how far you are away from home when you hire the car, and it may be limited to a certain number of continuous days per rental agreement. So check the details of the policies offered as well as comparing premiums. Try the following insurers:
Step 7: Think about the extras
Including an additional driver in the rental agreement will cost extra - check how much - and so will use of a child seat, roof rack or sat nav system. Book these in advance. You might be able to save money by taking a child seat with you - depending on your luggage allowance.
Step 8: Don’t forget the final checks
Before you head off, inspect the bodywork to make sure that any existing dents and scratches won't be blamed on you at a later date. Find out what the refuelling policy is - and, if you’re expected to return it with a full tank, where the nearest petrol station is. Finally make sure you’ve got the 24-hour emergency contact number for breakdowns.