Considering that there are more than a few of us here between the ages of 21-25, I thought it might be a useful contribution to the FT community to write a definitive guide to renting cars as a young twentysomething. Here goes.

Avis and Hertz do not rent to under 25s in the United States, period, unless you work for a company that has a special contract with either agency. However, there is a loophole for Hertz: if you join the American Bar Association as a "friend" ($150 or so per year) you're able to rent from Hertz as a 21-25 y.o. if you use the ABA booking code.

Budget's corporate locations require renters to be at least 25. However, many franchise operations have a minimum age of 23 or 21. Check www.budget.com for specifics.

Thrifty, Dollar, Alamo, and National allow young renters between the ages of 21 and 25 but charge a fee ranging from $10-$25 per day for the privilege.

Enterprise is the most liberal of all the majors when it comes to us younguns. You must be 21 to rent, but many locations don't assess a surcharge for under 25s. Those that do impose a fee typically only charge $10 per day extra.

Renting a car anywhere in New York or Michigan is possible for anyone over the age of 18 due to court decisions prohibiting age discrimination. However, be prepared to pay a hefty fee over and above the normal rental cost if you're 18 to 20.

My recommendation? National has provided the best service in my experience as a 22-year-old. Most locations are corporate-owned so there's consistency from city to city, and best of all many contract ID's (discount codes) reduce the underage fee to an easier-to-swallow $10 per day. Check the National board under "Car Rental Programs" for a long list of contract IDs. Also beneficial is a free Emerald Club membership, which allows you to bypass the rental counter and select the car of your choice from a special assortment of vehicles on the "Emerald Aisle." Emerald Club is a huge time saver, especially at busier airports.

Enterprise is also a good option, though the locations usually don't have a very large selection of cars and there's often a hard sell for the optional insurance. Staff is very professional, though---and I've found that at certain airport locations (notably Chicago O'Hare and Midway) they'll even match competitors' rates and waive one-way drop-off fees.

Speaking of insurance, be sure you have a major credit card, as most rental agencies do NOT accept debit cards. Since many of us have "student" credit cards with low limits, be aware that a few hundred dollars of your available credit may be taken as a security deposit until you return the vehicle. National only authorizes your card for the estimated amount of the rental, but Enterprise puts a hold for either $100 or $200 and Dollar a whopping $350 on your credit card. Be sure your CC isn't "maxed out" or otherwise you'll be forced to walk to your final destination

If you plan to rent cars frequently, try to get a Diners Club charge card. Diners provides primary collision insurance, an exclusive benefit that no other card offers. That means that no matter how expensive the damage to your rented car might be, you won't have to notify your personal auto insurance company and risk higher premiums. It's well worth the $95 annual fee in my opinion.

Second best for rental insurance is Visa. As of March 1, 2004, all U.S.-issued Visa cards, whether Classic, Gold, or Platinum, provide automatic secondary collision insurance for vehicles rented and paid for with the card. What "secondary" means is that Visa will only pay for the portion of the insurance claim that's less than the collision deductible on your own car's policy. If you drive an older vehicle and don't have collision coverage (or don't have a car at all), your credit card will cover you for the entire amount of the claim. Visa also pays for "loss of use" charges that are imposed by most rental agencies while a car is being repaired. Typically you will be charged for a full day's rental for each day the vehicle is in the shop to cover loss of use, which means Visa's benefit can be quite valuable if you happen to be in a serious accident.

American Express offers secondary collision coverage as well on all cards EXCEPT Blue for Students and Student Charge Card. However, AmEx does not cover loss of use, which makes it an inferior choice to Visa for car rentals.

MasterCard, to my knowledge, leaves it up to the issuing bank to determine whether there's rental coverage included. Read the fine print on your cardmember agreement carefully before choosing to rent with a MasterCard.

Discover's Gold and Platinum cards include secondary collision insurance for rental cars but like AmEx do not cover loss of use. Be aware that Discover Classic cards (as well as Student cards) have no car rental coverage.

Happy rentals, everyone!

(p.s. if anyone has experience renting cars in Europe under the age of 25, feel free to enlighten us! Most agencies there have a minimum age of at least 23).