SOME BRAVE FOLKS try to crack the code of Chesapeake Bay fishing all by themselves in their own small boats. But most of us rely on the wisdom of hired captains and the safety of their larger craft to put us where the fish are and supply the equipment to catch them.

Bay charter fishing is usually on boats rated for a maximum of six customers, and all-day trips generally cost close to $300, with half-days under $200. Larger boats accommodating groups of 15 or more are available, though harder to locate.

A charter trip can be wonderful or it can be a drag, depending partly on the availability of fish and partly on the skipper's congeniality, skill and willingness to adapt to the charterers' desires.

"The best thing is to find a captain you like and stick with him," says Mike Sullivan, president of the Maryland Charter Boat Association. He says a trust develops between a regular and his captain. The skipper won't mind telling regular customers when fishing stinks and they might as well stay home, and will make a special call when things heat up.

He's also more likely to say "why not?" when a regular charterer comes up with a screwball idea such as trying to catch flounder on a fly or running up some uncharted creek in pursuit of a purported school of jumbo spot.

Following is a month-by-month calendar of the summer fishing season in the Maryland portion of the Bay, the waters most accessible to area fishermen. There's fine fishing south of the state line in Virginia, as well, but the long voyage to the boats makes Virginia a destination for hard-core anglers who shouldn't need advice.

Included in this calendar are some ideas of places to try in the early, mid-ebb and flow with the weather. Some skippers are mentioned, most whom come well recommended.

But this is only a loose guide, and there is no guarantee that he who fishes with a recommended skipper in a recommended area at the recommended time is going to load up the fish box. As in love, there are no guarantees in fishing. MAY

The traditional opening month of the Bay season has suffered from the moratorium on rockfish, but big bluefish remain an excellent quarry for the early-season angler. The largest blues arrive first, on their way north to summer feeding grounds off Long Island and New England.

May bluefish are called "all head" by veterans because while their heads are large, they are slender through the body from a winter of fasting. They generally travel solo and are ravenously hungry. They are scarce enough that on a good day you're lucky to boat four or five, but they'll be the biggest blues you see all year, running up to 14 pounds and better.

The blues' history in the Bay is interesting. Twenty years ago, a four-pound bluefish was a rarity worth photographing. Some old-timers remember years when hardly a bluefish was seen, back when rockfish ruled the Chesapeake.

You may boat a big rockfish while bluefishing, by the way, but it must be turned loose.

You can fish close to home for big blues in May. Try the Rod 'n' Reel Dock in Chesapeake Beach (D.C. area phone number 855-8351), or one of the booking houses out of Deale, all of which also have D.C. area tie lines (AAA Charters at 261-5656; ABC at 261-5353; Happy Harbor at 261-5297).

If you don't mind driving across the Bay Bridge, Kentmorr Harbor at Grasonville books charters at 301/643-4201,as does Buddy Harrison's Chesapeake House in Tilghman (301-886- 2121). JUNE

Last year wasn't as good as most, but the folks at Solomons Island, a 11/2-hour drive south of Washington at the mouth of the Patuxent River, hope the traditional June run of big sea trout returns this season.

The Solomons fleet is adventuresome, anyway. If trout aren't running well, they might run across the Bay aftr flounder, or up the Patuxent to try bottom fishing for spot and perch, or they might chase schools of bluefish breaking water, and have their anglers cast to the schools with light tackle.

"Breaking blues are common in June," says Capt. Bob Clark, "and casting to them seems to be what the public really enjoys."

The sea trout generally stay in deeper water and are caught by trolling or jigging with light tackle. Like the blues, they've come on strong in recent years. Practically no one caught a sea trout in the middle and upper Bay a decade or more ago, but for several years these reddish-gold predators have been common, with many in the 10-pound-and-up range.

Solomons bookings aren't quite as organized as those up the Bay. Some skippers to call are Clark (301/326-3582); Robbie Robinson (301/326-3998); Bunky Conner (301/535-5271); and Jack Johnson (301/326-3241).

Also, sea trout parties are booked with good results a little farther south out of Trossbach's Marina near Point Lookout (301/872-5321). JULY

High summer is bottom-fishing time in Crisfield, which is three hours plus from Washington and worth every minute of it when the fishing is right.

"It's the best bottom-fishing place anywhere on the Bay because of the variety," says Sullivan, who ticked off the species available: "Spot, croaker, trout, flounder and bluefish."

Charlie Mariner, who skippers one of the Crisfield boats, says last year was particularly good for flounder, but an off year for trout. He says the best place to call to book charters is Somers Cove Marina, 301/968-0925, and ask for Irma. "She has the list," he says. AUGUST

This is a good month to seek refuge up the creeks, pursuing little fish and a breath of cool air from the shady banks. The Optimist, the headboat operating out of Chesapeake Beach, runs daily up the Choptank River in pursuit of white perch, charging $17 a day per person. The D.C. area phone number is855- 7760.

Also, there's good fishing on the pilings of the Chesapeake Bay Bridge for perch and spot, and this water is accessible to small boats you can rent at Sandy Point State Park (301/757- 9893).

The Wicomico River off the lower Potomac offers terrific perch, spot and croaker fishing, with small boats available for rent at Quaid's Store (301/769-3903).

And some charter boats operating out of Solomons Island will run up the Patuxent River to bottom-fish hotspots there. Call H.M. Woodburn's (301/326-3241). SEPTEMBER

It's everyone's favorite month. Bluefish abound in September, and there's no place quite as exciting to fish for them as off Point Lookout, where the charter captains use chum to attract schools of hungry blues and fishermen get to tangle with them using light tackle. The boats often bring in more than a hundred blues a day. Scheible's Fishing Center in Ridge specializes in this sort of fishing, and scores well all summer, though September and October are always best. Call 301/872-5185.

Trolling for blues also is excellent this time of year farther up the Bay, out of Deale, Chesapeake Beach, Tilghman and Kentmorr. In fact, according to Sullivan, there is just about no place in the Chesapeake that you can't catch a bluefish as the season draws to a close.

One last caution: Remember, this year for the first time a $5 Chesapeake Bay fishing license is required in Maryland portions of the Bay. Don't get caught without one.