Heading to the beach for Memorial Day today, or planning a big summer vacation?

The choices you make about how to get there could have an impact on the environment as well as your wallet.

Travelers are increasingly asking for tips on how to make their trips "greener," said Bob Schildgen, an advice columnist for Sierra Magazine, published monthly by the Sierra Club. Many of the pointers Schildgen offers also could lower your travel costs as gas prices near $4 a gallon.

His biggest tip?

"Don't drive a gas-guzzler anywhere," he said, suggesting that on trips, travelers consider renting a smaller, more fuel-efficient car or hybrid that will take you farther on a gallon of gas and create fewer of the greenhouse gas emissions that cause global warming.

"You could come out ahead financially by saving all that money on gas, even when you add in the cost of the rental car," said Schildgen, author of the new book "Hey Mr. Green."

You also can make your own car more fuel-efficient before you head out on your road trip.

"Tuning our car and inflating our tires are simple things people can do to save money and cut pollution," said Deron Lovaas of the Natural Resources Defense Council.

Motorists also can burn less gas by obeying the speed limit, Schildgen said.

"You're on vacation, what's your hurry?" he said. "You'll burn up a lot more gas going 90 miles per hour than going 50 miles per hour."

If you're planning a summer trip that can be taken in segments, consider doing some of it by train — for example, from Las Vegas to the Grand Canyon, or from New York to Boston.

Trains are by far the most energy-efficient way to travel, followed by cars and then planes, according to the U.S. Department of Energy.

Amtrak spokeswoman Karina Romero said the passenger train service is beginning to emphasize that fact as people show more interest in doing their part to reduce global warming.

According to Amtrak's Web site, carbon emissions created by a plane from San Francisco to Los Angeles are nearly twice that of a train going the same distance. The emissions from a car on that trip are a little higher than the train but significantly less than the plane, Amtrak's chart shows.

If you need to fly, opt for the nonstop flight whenever possible, because planes burn more fuel on takeoffs and landings than they do at their cruising altitudes, energy experts say.

Many travel-booking Web sites also offer their customers a chance to make a small donation to a green energy company to help offset the global warming effects of flying. If you opt to do that, check out the energy company to make sure it's legitimate, Schildgen suggests.

Finally, consider staying close to home while on vacation. As people try to save money on gas this summer, some state tourism boards have mounted campaigns to persuade their residents to do just that. That could help the environment, too.

"A lot of us don't explore our own areas very well," said Schildgen, who lives in Berkeley, Calif. "Something in your own backyard might be just as exciting as something far away."

Learn more:

www.sierraclub.org/sierra — click on "Hey Mr. Green"

www.amtrak.com — Amtrak; search for "carbon offsets"

www.doe.gov — U.S. Department of Energy.

www.gasbuddy.com — compare regional gasoline prices