Even worse than the expense of renting a car are all the little details you need to consider when signing a rental agreement. You've got to think about such things as how you'll pay for gas, what you'll need for insurance, and what rules and restrictions the rental agency demands. Our checklist of car rental do's and don'ts will ensure your experience is a good one.

See also: 5 ways to save money when you rent a car.

Mind these car rental tips and avoid getting burned by all the little details. — Photo by OJO Images/Getty Images

Compare rates on rental agency and travel websites. Be sure that any "deals" really are deals: Sometimes a rate really isn't so great after you tally all the fees and taxes. Asking for AARP-member discounts could save you up to 20 percent, while AAA and travel loyalty programs can also trim costs. Checking coupon sites, booking compacts and avoiding "extras" like satellite radio are other ways to save. Consider collecting your car at a location other than the airport to avoid those fees. And be wary of rental agency gas tank fill-up packages; some quick math, depending on prices at the time, will help you determine whether filling up yourself is the better option.

Booking early gives you flexibility — both in terms of choice and pricing. Longer lead times mean more available cars, a broader selection and better rates. Arrive early, or at least on time, when returning a rental car. Even slight tardiness can cost you an additional day.

This bit of car rental advice seems obvious, but think: Do you really need a rental car? Paying for a rental, gas and parking doesn't make sense if you'll spend most of your vacation lounging on a beach or exploring city streets. Consider renting only for a day or two and using public transportation and cabs the rest of the time. On the other hand, if you lease your existing family car, and you're planning a long road trip, renting makes sense for avoiding costs associated with exceeding the lease's annual mileage cap.

It's highly likely you are already covered for a rental car on your existing policy, but check first with your insurance agency, buying only supplemental insurance as needed. At the very least, you need good collision-and-damage waiver (CDW) insurance. Some credit cards also offer CDW when you use them to charge car rentals.

Most, but not all, U.S. agencies allow you to cross into and drive around Canada. There might be some restrictions and insurance issues, however, so ask before heading to the Great White North. Meanwhile, down south, driving into Mexico is forbidden by American-based agencies. In addition, some agencies have restrictions on back-country driving, say, or taking cars into major metropolitan areas. Be aware of those restrictions before taking that Land Rover for a desert jaunt.

Walk around the car, noting any dings, scrapes or dents. Use your camera or smartphone to take pictures or video of any damage (or lack thereof). Point out damage to the rental agent and ask him or her to note it on the paperwork. If you encounter any pushback, or the damage seems extensive, request another car.

Also of interest: Be a safe driver; get tips and take a course.