Getting the best deal on a rental car has always been complex.

These days, it's getting trickier.

As everyone from rental companies to online travel agencies fiddle with features and pricing strategies, it's getting tough even for seasoned travelers to decode the best deals.

Cendant Corp.'s Avis Rent A Car offers six different types of insurance and damage waivers. Ford Motor Co.'s Hertz has 26 different car classes, eight of which consist of a single vehicle. Due to a lack of industry pricing standards, companies can, and do, charge differently for the exact same cars.

Meanwhile, add-on fees, designed to finance projects like airport expansions and new sports arenas, are multiplying like stale fries on the floor mat.

In Texas, Gov. Rick Perry recently signed off on a proposed 6 percent car-rental tax in Dallas County to help pay for a possible new stadium for the Dallas Cowboys football team -- on top of the 5 percent car renters in Texas already pay to cover construction of the American Airlines Center, which is home to the Dallas Mavericks basketball team.

California recently approved a bill that requires rental-car companies to collect an extra 2.3 percent fee; as part of the deal, rental companies also will be allowed to include a separate charge covering state vehicle-license fees, which tripled last summer.

It's happening as airports, municipalities and of course, rental-car companies, look for ways to boost revenue amid a travel slump. Rental companies have rolled out an array of new options, from in-car satellite radio for an additional charge, to special online sales packages designed to encourage renters to bypass the rental counter and book online.

Even casual travelers know you generally should decline the extra insurance, since you're usually already covered by your own insurance. But saving serious money when renting a car increasingly requires an insider's knowledge of the intricacies of the car-rental game.

Here's our guide to knowing when, where and how to rent a car to get the best deal possible.

  • Book early and often. Booking early and often is the key to saving money. According to Travelocity.com, most travelers book airplane tickets and hotel rooms 21 days in advance, and 10 days in advance, respectively. However, they wait until just a week before a trip to book a rental car.

    That's a mistake. Unlike airlines and hotels, rental-car firms don't charge penalties for cancellations. As a result a good way to lock in the best deal is to make a reservation early, whenever you spot a good price. Then, keep shopping around and if you see a better one, book it and cancel the first one.

  • Play the date game. During most of the year, renting vans, pickup trucks and sport-utility vehicles during the week can save money, since demand for large vehicles is higher during the weekend.

    Conversely, renting luxury cars such as Lincolns during weekends is cheaper because demand for those cars is higher when road warriors travel on weekdays. And like airline tickets, renting a car with a Saturday night included can save money.

    "Oftentimes, you're going to find aggressive weekend rates because the companies want you to stay over Saturday," said Phil Kennewell, Travelocity.com rental-car expert.

    Sometimes, getting the best deal on a rental can seem counterintuitive.

    For instance, even if you only need a car for five days, it's worth seeing if you can end up paying less if you take the weeklong rate. For example, a midsize car rented from Budget Rent A Car at Dallas-Fort Worth International Airport recently was $55.99, or $279.95 for five days, compared with the weekly rate of $144.99 at the same rental company.

  • Know what you want. This is one of the toughest decisions. Making it worse is that the same car can be in different classes at different companies -- and even at different locations of the same company.

    For instance, a Pontiac Grand Am is "midsize" at Avis, but classified as a larger and pricier "standard" at Enterprise. And pricing is all over the map.