Are you thinking about buying a camera for a Christmas present? A stereo system to give yourself? A basketball for the kids?

If so, chances are you might plan to stop by one of the retail catalogue showrooms here of Best Products Co. or W. Bell & Co. In general, these two companies are 11 percent to 14 percent cheaper for key photographic equipment items than many stores that specialize in such products. p

But wait! Nothing's that easy. At the discounter, for example, you may not get much help when you ask for advice on setting up a darkroom.

Moreover, when you start to look for the stereo equipment, you'll find that Reliable Home appliances may undercut Best by 17 percent and Bell by 14 percent. Luskin's, Circuit City and other stereo specialty shops also have lower prices than the big discounters.

As for the Wilson NBA leather basketball, prices surveyed recently ranged from a high of $51.99 at the Sportsman to a low of $36.96 at Memco.

These are some of the pieces of information a consumer could gather by shopping around. But unless you have unlimited time to make telephone calls to dozens of stores for price quotations -- and to make trips to some stores where sales people aren't too helpful over the telephone -- the chances are you won't use up the car's gasoline traveling around the Beltway, looking for the best buy on every single purchase.

For these reasons, many area residents will welcome a young newsletter venture of the Washington Center for the Study of Services. The center has gained attention for its Washington Consumers' Checkbook nonprofit magazines, which have studied in great detail the prices and quality of service at such area businesses as automobile repair shops and grocery stores.

Now it has started the smaller newsletter, called PriceFighter, to offer guidance in the search for bargains.

The second issue, out this morning, concentrates on photo equipment, sporting goods, stereo stores and home heating oil prices. Among the conclusions:

Washington is a "bargain capital" for stereo equipment, but the stereo stores remain sharply divided into two types of operations, discounters and "salons," with each selling different product lines. At discounters, prices vary 25 percent or more, but among the fancier shops prices are fairly uniform.

In those few instances where both types of stores had the same merchandise, discounters' prices were substantially lower.On the other hand, customers surveyed by the center rated service of the salons far higher than at most discounters.

Camera bugs have a more difficult time finding bargains in the Washington area. Indeed, mail order shopping from photographic stores was recommended (even by a local retailer). The center said prices at some New York shops averaged 13 percent to 14 percent below the average of Washington-area retailers and up to 7 percent below the lowest local prices, which were at Tanen Sales Co.

Baker's Photo Supply Inc. (highest average prices here), Falls Church Camera Shop, National Camera Repairs & Sales and Rockville Photo Center were top-ranked for service, winning "superior" rankings from at least 90 percent of customers surveyed.

Herman's World of Sporting Goods and Irving's Sports Shops, two big sporting goods chains, were strong in terms of having the greatest variety of goods. But neither was tops in price or advice.

Basco, Bell, Best and Major Sports were 13 percent cheaper than Herman's and 15 percent cheaper than Irving's but none of these lowest-priced stores carried more than 24 percent of a 59-item sports goods market basket. For advice, the standouts were The Sportsman and two specialty shops, Athlete's Foot and Racquet & Jog.

The price of No. 2 home heating oil (as of Sept. 23, for a house with a 275-gallon tank) ranges from a low of 96 cents a gallon at Amerada Hess Corp. to a high of $1.05 a gallon at six firms -- Colonial Fuel, Hessick, Washington Coal, E.J. Read & Sons, Griffith Consumers and Amato.

The 9-cents-per-gallon savings for a Hess customer is worth $108 on an annual heating bill for a typical area household that burns 1,200 gallons a year. Hess has had the lowest price in every survey made by the center for its publications.

Southern States Co-op (serving only Northern Virginia), at 99 cents a gallon, also is a bargain since profits are distributed to customers at the end of the year (the rebate last year was worth some 4 cents a gallon).

The newsletter that includes these reports is available for $1 from Washington Consumers' Checkbook, Washington Center for the Study of Services, Suite 406, 1518 K St. NW, Washington 20005.

Another publication of the center, selling for $3.65 including postage, is a guide to 1981 health insurance plans for federal employes.