When outsiders think of Baltimore, the white marble steps, seaport and sports teams immediately come to mind. But what is overlooked is the charm, the hometown camaraderie that exists in this large cosmopolitan city. Baltimoreans are talented, involved individuals with a penchant for enjoying themselves, and the activities and the sites within the city reflect this attitude. TRANSPORTATION

The subway system is a long way in the future, but travel by car is fairly smooth if you avoid the Baltimore-Washington Parkway and Jones Falls Expressway during rush hour. Buses offer one means of exploring the various sections of town. Taxi service is adequate, but if you have a car use it - the city is fun to explore at leisure without a meter ticking away, and parking is cheaper than in Washington. Both Greyhound and Trailways maintain bus terminal in the city. Trains are a possibility as well, but Baltimore's Pennsylvania Station, although historic, has changed little over the years: It retains its dingy, rather dreary atmosphere. THINGS TO DO

Walk around Lexington Market with its square block of seafood stalls, produce counters, bakeries and delicatessens boasting every food available from farm, dairy or sea. Then wander down to the Inner Harbor and tour the U.S. Frigate Constellation, open daily 10 to 3:45, Sundays to 4:45. (Adults $1, children 6 to 11, 50 cents.) Baltimore is foremost a port city, so take in the water, the ships and the smells of the McCormick & Co. spice plant just half a block away. Then, of course, there's Fort McHenry, which came to national prominence when it was attacked by the British during the War of 1812. At that time a lawyer named Francis Scott Key wrote "The Star-Spangled Banner." The fort is open daily 9 to 5.

For the religious in spirit, the Mother Seton House is open weekends, 1 to 4; the first American-born saint occupied the house from 1808 to 1809. In the same vein, you can visit the oldest synagogue in Maryland. Dating back to 1845, the Lloyd Street Synagogue is open on the first and third Sundays of the month, 1:30 to 4.

Special events this month include the second round of a scrabble tournament Jan. 22 and its finals Jan. 29; the tournament is sponsored by the Mayor's Office of Special Projects and The Evening Sun. SPORTS

The sports events that mesmerize thousands of fans are the Colts and Orioles games held at Memorial Stadium. In May the Preakness is held at Pimlico racetrack, fostering a week of activities ranging from parades to the Mayor's Annual Preakness Frog Hop. RESTAURANTS

Aahh . . . don't, I repeat don't, miss the tastes of Lombard Street's Corned Beef Row, Little Italy's abundance of pasta-filled dishes, Tio Pepe's famous Spanish cuisine (if you can get a reservation), the Greek restaurants Athenian and Ikaros on Eastern Avenue, the Chespeake or Danny's or The Prime Rib for more classic fare. The best crab houses are Gordon's of Orleans Street, Bud's Beer Garden, The Pump Room and Obrycki's Seafood Restaurant. If you can, still move, try one of the new French restaurants causing a stir - Cafe des Artistes and Chambord are the best. For good seafood and ethnic dishes, Baltimore's tables are laden with a fabulous selection. MUSEUMS

The Baltimore and Ohio was the first railroad in this country. Its original Mount Clare Station is now a museum housing a collection of cars and locomotives dating as far back as 1829. the streetcar played an imtegral part in the city's history from 1880 to 1963 - the Baltimore Streetcar Museum has a collection of cars depicting the evolution of this public transportation system; you can even pay to take a half-mile ride on an antique car.

The Baltimore Museum of Art currently has several special exhibitions in addition to its permanent ones: "Delights of the East," through January, reflects the arts of China, Japan, India, Nepal, Tibet, Burma, Thailand and Cambodia; and an exhibition of photographs by Andreas Feininger is on display through Feb. 12. Walters Art Gallery and B.R. Kornblatt Gallery are among the finest in the city. And while you're driving around town, look for the 40 outdoor neighborhood murals painted by local artists under the sponsorship of Mayor Schaefer's Office of Manpower. NIGHT LIFE

Since Alexander Cohen became the impresario of the Morris Mechanic Theater, show biz is a big business in Charm City. "Chicago," starring Jerry Orbach, will run through Feb. 4. Intimate theater of the highest caliber can be found at Center Stage, which offers "The Runner Stumbles" through Feb. 12, followed by Tennessee Williams' "The Night of the Iguana" Feb. 17 to March 19. "Ashes" by David Rudkin will follow March 24 through April 23; it's a brilliantly provocative, risque British drama about a couple unable to conceive a child.

Fells Point ias an area popular with artists because of its low rent, antique shops and galleries by day, a proliferation of bars at night (including the popular Barge nightclub). The Mount Vernon-area bars are also quite popular, including Uncle Charlie's Bistro, Longfellow's, Owl Bar and Brass Elephant. For good live bluegrass, jazz and pop music, try such clubs as Congress Hotel Marble Bar on Franklin Street and No Fish Today on North Eutaw. Peabody Bookshop and Beer Stube (Mount Vernon area) was a speakeasy during prohibition, with H.L. Mencken a frequent customer.

If you can stay up for it, take the Insomniac's Tour of teh city: a bus tour beginning at 1:30 a.m., this all-night excursion includes a late-night visit to the grave of Edgar Allen Poe in Westminister Church and a windup stop at Fort McHenry as the flag is raised at dawn. (Check with Baltimore Rent-a-Tour, 653-2998.) Or there's "the Block" - a section of Baltimore Street with pornographic bookstores, peep shows and strip-tease joints.

At the Lyric Theater, the Baltimore Symphony under Maestro Sergiu Commissiona offers assorted concerts: jan. 20 - Nicolai - Overture to Merry Wives of Windsor, Schumann - Cello Concerto, and Tchaikowsky - Symphony No. 4; Jan. 28 - Musical Theater Promenade, a medley of Broadway favorites.