Greg Gumbel is the kind of guy you'd talk to at a cocktail party: He drinks beer from a bottle, tells Rodney Dangerfield jokes, recalls all eight Rolling Stones concerts he has attended, and admits that he's a little nervous about hosting CBS' Winter Olympics coverage from Norway. First of all, he hates the cold. Second, after 21 years in TV he's taking on his biggest assignment. Not to worry, though. Gumbel has been priming for the sports schmooze business since prepuberty. As kids in Chicago's Hyde Park, he and younger brother Bryant (now a Today show cohost) took turns standing before a mirror, pitching and doing play-by-play for a simulated nine-inning game. The major- league career never panned out, but the one in broadcasting did, beginning with a sports-anchor job at a Chicago TV station in the early '70s. His on-air assignments now include hosting NFL Today and calling play-by-play for baseball and basketball. Unlike his baby brother, the 47-year-old Greg comes off as an easygoing sort. ''He's knowledgeable, articulate, and funny,'' says Rick Gentile, CBS Sports' senior vice president of production. ''A nice guy to hang out with. What Greg is in real life, he is on the air.'' The real-life Gumbel is also a husband (wife Marcy is his business manager) and a father (daughter Michelle is 24). Gumbel's secrets of success-like the man himself-are relaxed and uncomplicated: 1. Don't take yourself too seriously. (''I don't pretend I'm more important than the broadcast-that was Howard Cosell's huge failing.'') 2. Enjoy a good joke (and be able to retell it afterward). 3. Catch Howard Stern in the morning. (''People ask me if I watch Today. Why would I want to hear Bryant in the morning when I shared the same bed with him for years?'') 4. Do your homework. Lately that last rule has been especially important: Gumbel devotes a few hours a day to Olympic cramming and meets weekly with CBS researchers. ''They're my guardian angels,'' he says. ''I'm trying to get them T-shirts that say, 'I saved Greg's ass in Norway.'''