Shopping for a good beach is a lot like shopping for a good car: You need a good idea of what you want before you can be pleased with what you get.

That's why Stephen Leatherman, a professor at Florida International University, is a lot like the favorite mechanic to whom a car shopper might turn. Known as "Doctor Beach," he ranks America's beaches by dozens of attributes to form a Top 20 list of beaches every year.

"I got involved in beach ratings when a travel magazine editor in 1989 wanted me to give him my Top 10 List of U.S. beaches," Leatherman recalls. "He said he needed something for a sidebar, nothing really important. So I just popped off 10 great beaches that I knew, the article was later published in this glossy magazine, and then I started getting all of these calls from tourist bureaus and CVBs who wanted to know why their beach wasn't on this list or thanking me for their beach appearing on 'my list.'

"The phone rang off the hook for over a week. I then realized that this ranking thing was really important to beach communities."

"Dr. Beach" then went to work to produce his book, "America's Best Beaches."

He spent two years -- 1989 to 1991 -- developing the 50 criteria to rate beaches and actually using those criteria on the 650 sites. Professional coastal managers in every state help to keep him informed and up-to-date, but he has visited all of the beaches personally -- and he has some 60,000 color slides to prove it.

"Fortunately," he says, "I had undertaken two national surveys of our coasts for federal agencies (Department of the Interior and the Environmental Protection Agency) in earlier years, so I was in the unique position of having seen all of the beaches and could undertake this rating."

Leatherman's latest chief Cadillac among America's beaches is Kaunaoa Beach, on the Big Island of Hawaii, which tallied high marks in all 50 of his criteria. Those criteria comprise three main categories: physical factors, such as sand softness, wave size and current strength; biological factors, such as water color and quality and the presence of pests; and, human-use factors, such as lifeguard protection, visual obstructions and amenities.

Kaunaoa was cited particularly for its "great sunny beach weather."

"This long crescent-shaped, white sand beach contrasts with the black lava headlands that frame it," Leatherman says. "It is a great place to swim and snorkel in the sparkling clear waters, especially during the calm summer months."

The beach at St. Joseph Peninsula State Park is known for its miles of white sandy beach and striking dune formations. Photo courtesy of FLAUSA

Leatherman also ranks beaches by attribute. What's the best walking beach, featuring hard-packed sand and gently sloping beaches? That would be Gay Head on Martha's Vineyard, Mass., followed by Hammocks Beach State Park, N.C. The best of the wild beaches -- sparsely populated with limited access and abundant in nature -- is Jasper Beach in Maine, followed by Cumberland Island, Ga. At the head of the "best romantic category" -- those beaches featuring natural beauty, privacy, good sand and water quality and such amenities as easy access, picnic areas and places to walk along shore -- is East Hampton, N.Y., followed by Kiawah Island, S.C.

Excursia.com destinations are well represented in Leatherman's Top 20 rankings. They are:
St. Joseph Peninsula State Park (ranked #2)
Located near Port St. Joe in Florida's panhandle, St. Joseph features miles of white sand beaches and striking dune formations. The park, which comprises 2,516 acres and a heavily forested interior, is bounded on three sides by the waters of St. Joe Bay and the Gulf of Mexico.

Caladesi Island State Park (#6)
Visitors to this six-island, 1,750-acre park at Dunedin, in the Tampa Bay area on Florida's central west coast, like its serenity and seclusion. It also is well-endowed with amenities, including picnic pavilions, bath houses and a park concession. Ferry service from the mainland is available hourly when weather permits.

Fort DeSoto (#7)
Also in the Tampa Bay area -- 10 miles from downtown St. Petersburg, to be exact -- is this 900-acre preserve with seven miles of pristine beach. There's little development yet such enticements as a canoe trail and a 4-mile paved trail for cyclists and skaters to boot. Younger visitors like to explore an 1898-era fort.

Bill Baggs Cape is home to the historical Cape Florida lighthouse. Photo courtesy of FLAUSA

Bill Baggs Cape Florida SRA (#9)
A wide, 1.25-mile beachfront that offers excellent swimming in the Atlantic is one lure for Miami-area residents at this state recreational area at Key Biscayne. You can choose a visit to a historical lighthouse (the oldest building in south Florida), an afternoon of saltwater fishing or a shaded picnic in one of 18 covered pavilions, too.

St. George Island State Park (#11)
Located at Eastpoint in Florida's panhandle, St. George is hailed for its natural features: extensive beaches and dunes, forests of slash pines and live-oak hammocks. The ocean and bay provide an abundance of marine habitat; in fact, the waters here are home to some of the most productive commercial and sport fisheries in Florida.

The beach at Perdido Key. Photo courtesy Pensacola Convention and Visitor Information Center

Perdido Key State Recreation Area (#14)
The panhandle strikes again -- this time on a 247-acre barrier island that's 15 miles southwest of Pensacola. Wide, white sandy beaches and rolling dunes covered with sea oats provide habitat for shore birds and other animals, and they also present unique opportunities for visitors to swim, relax, fish or simply enjoy nature.

Siesta Beach (#15)
Known for some of the finest and whitest sand in the world, this 6-mile-long beach on Siesta Key is popular for walking because of the shallow depths that extend hundreds of feet offshore. And on those occasional winter days when the temperature drops, the warm water from the Gulf of Mexico keeps this Sarasota-area isle warmer than what one will find inland.