Most state laws guarantee you a car if you have reserved one. When you make a reservation always get a reservation number, and show up within a half hour of the time, the company is required to give you a car of the similar size or give you a upgrade if the one you reserved is not there. Or they must pay your transportation to another agency; the original car rental agency must pay any increase in cost.

Basics:

1. Use toll free numbers to comparison shop. Look for weekly and week-end specials.
2. Ask if there are any pick-up and drop-off fees at the location you will be using.
3. Find out about any blackout days that could affect an advertised special.
4. Ask about the weekly rate if you are considering a rental for more than 4 days. The daily rate for rentals of more than 4 days, but fewer than seven, is often higher than renting a car at weekly rates.
5. Ask about mandatory additions to the quoted prices, such as mileage rates and caps, fuel charges, airport surcharges, and taxes. Also ask about optional charges when they're applicable, such as additional driver's fees, underage drivers' fees, out of state charges, and equipment rental charges. Always check the gas policy. Often you have to return the gas tank full. If you forget to fill up, agencies charge a substantial markup.
6. Ask about charges for optional collision damage waiver (CDW), personal accident insurance (PAI), and personal-effects coverage (PEC, also known as personal effects protection, or PEP). Know whether your own auto-insurance or credit-cards cover these, but beware! Up to 25% of rental car claims against credit cards are rejected because of violations to the contract; a second driver was not listed on the rental agreement; the driver's license has expired; or the driver was speeding.
7. Your best bet is your home owner insurance. Some-for instance, Chubb in New York-covers rental cars. If you own and insure a car call your agent to find out whether your policy covers rental cars. The deductible is usually much less for rental cars, so don't let them tell you otherwise if it is written in your contract.

The first thing I tell people is don't pay the asking price. That means, don't just walk up to a car rental counter and ask for the price. You will always get ding'd if you do that. Instead, find a computer that is connected to the internet and book it online.

If you are looking for a cheap rental, check out Dollar, Thrifty, Budget and Enterprise. Each of these companies provide pretty new vehicles at their locations for a low rate.

1. The first place when you reach the company's website to check is their Specials page. Depending on how long you need your vehicle, check if there are any dollar savings off a weekend, weekly or monthly rate. Most of these specials are in the form of a promo code or discount code. Take note of it before you leave the page.
2. If you work for a large corporation, check with your company and see if they have a preferred car rental agency and what the discount is. Most large corporations have corporate accounts with Hertz or Avis, and not any of the discount ones that I have listed. With the right corporate code, you may be able to get better rates with their companies or you may get special privileges. I would compare the prices with these discount companies just to see which one offers the better deal.
3. If you don't have a corporate code then ask your friends if they know of any. For example, if you belong to Costco, they have codes for Alamo, Budget, Avis and Hertz. And if you golf and belong to the USGA, you can use their special code for Hertz. (I believe the last time I looked, the code was printed on the USGA site under benefits.) Having a code will save you up to 25% off your total rental costs.
4. When you pick up your car, stay firm on your booking. Because their rates are substantially discounted, they will try to encourage you to upgrade the vehicle for an additional cost. Or if they ran out of the size that you had booked for, they will try to charge you for a larger size car. Either way, stay firm and demand that they honor your booking.
5. Check with your car insurance company and credit cards to see if there are any car rental coverages that are included. For instance, most gold credit cards offer comprehensive coverage on car rentals. This will save you up to $10 per day if you decline the coverage from the car rental agencies but remember to use the gold card to pay for the rental. Also, some car insurance policies allow you to take the coverage you have on your home vehicle and transfer it to the rental car. This could potentially save you another $20 per day.

I personally take no coverage when I rent because my AllState insurance allows me to take my coverage and transfer it to the car rental and my gold American Express card covers the liability. I have to stay firm at the counter, and decline their coverages and not flinch when they say I am responsible for the whole car in case something happens to it. I know AllState and American Express are behind me on it.