* SATURDAY 31st Ryder Cup Matches (NBC, 8 a.m.-12:30 p.m.; 4-6:30 p.m. EDT): Dick Enberg hosts this biennial golf tournament live from Oak Hill Country Club in Rochester, N.Y. The match's format, which includes 12 players each from the United States and Europe, is quite different from others: The morning telecast features teams of two players who alternate shots on the same ball. In the afternoon, each of the two players on a team plays his own ball, with the better score of the two counted. * SUNDAY 31st Ryder Cup Matches (NBC, 9 a.m.-3:30 p.m. EDT): The conclusion of the golf tournament features head-to-head play - a dozen 18-hole individual matches. The Searchers (The Family Channel, 7-9:30 p.m.): John Ford's classic 1956 western, starring John Wayne and Natalie Wood, will be showcased this evening and two later dates: Wed., Sept. 27 at 6:30 p.m. and Sat., Sept. 30 at 8 p.m. * MONDAY The Popular Mechanics Show (Discovery, 5-6 p.m.): How do you unstop a clogged garbage disposal? What's the best way to stack wood in a fireplace? When should you use the emergency brake in a stick-shift car? This new daily series answers these questions and explains the mechanics of other everyday objects. Recurring guests include experts in computers, home improvement, aviation, landscaping, automobiles, and barbecuing. History's Turning Points (The Learning Channel, 8:30- 9 p.m. EDT): Unexpected twists and turns have altered the course of human events over the past 2,000 years, and this new daily series seeks to illuminate these mileposts. Viewers will visit such settings as ''The Great Wall of China,'' ''The Conquest of the Incas,'' and ''The Siege of Constantinople.'' This premiere episode, entitled ''Pocahontas's Marriage,'' explains how a native American woman's union with colonist John Rolfe gave the English a foothold in America - and eventually led to the Revolutionary War. Please check local listings for these programs.