TAMPA, JAN. 26 -- The Giants and Bills both held light practices this morning, then began what New York Coach Bill Parcells called "the longest part of the week."

He said, "It seems like forever until the game. That's the real waiting because you're just filling time, and you're not filling it with anything really important."

The Giants were on the field at Tampa Stadium about 30 minutes this morning. They also posed for a team picture.

"I'm pleased with the way things went," Parcells said. "I think our team's prepared to play, and I think we'll play hard. It doesn't mean we're going to win, but we'll give it our best shot."

The Bills worked on kickoffs and substitutions during a 30-minute practice. Tight end Butch Rolle (ankle) practiced for a second straight day and Coach Marv Levy said he's "fine and should be ready to play."

The Bills began the week with 46 players, but went to 47 today by activating linebacker Matt Monger from injured reserve. He fills the spot created when linebacker Marvcus Patton suffered a broken leg in the playoff opener against Miami. Monger probably will be on the two-man inactive list for the game.

Levy said his players have "done their work and now they're looking forward to the game they've waited to be in all year. They feel good. They're in a good mental state. Saturday night is usually the easiest night of the week for me. I'll do a little studying and re-examining of the notes I took."

A pair of former Buffalo quarterbacks, Joe Ferguson and HUD Secretary Jack Kemp, attended the practice. Kemp spoke briefly to the team. Rain, Temperature to Fall

The National Weather Service says game-time temperature will be about 70 degrees with a partly cloudy sky and a chance of showers. Temperatures are expected to drop into the fifties during the game. . . .

Lawrence Taylor on the Bills' no-huddle offense: "The key is not in trying to stop their great players, but in slowing them down. They can run up and down the field all they want, but it doesn't matter if you don't let them score after they get down there in the red zone." . . .

Bills center Adam Lingner says Levy sometimes sings to the team before games. Before last Sunday's AFC championship game, he did a rendition of "One More River to Cross."

"He's a better coach than a singer," Lingner said. Remembering Homeless

Among the parades, street festivals and concerts in Tampa leading to the game is a special bash just for the homeless. Beginning today, local advocacy groups are throwing a Super Bowl two-day party at a day center for the homeless.

Tonight, Frank Sinatra sang at the Sun Dome while Whitney Houston appeared at Bayfront Center in St. Petersburg. On Sunday, the Florida Orchestra becomes the first orchestra in history to perform at a Super Bowl, according to the NFL. The orchestra will perform the national anthem, to be sung by Houston.

For fans hunting unusual souvenirs, there was an "end zone" cat litter box stamped Buffalo Bills on the side and a squeaky toy resembling an NFL referee.

The refs, at half the price, were said to be selling better.