On recent National Football League draft days, the art of trading has become as vital as the art of scouting. It's a cool game of smooth moves that often ruin another team's best-laid plans. Remember how the 49ers, set to pick last, gave up their three top picks to New England last draft day to take awe-star receiver Jerry Rice with pick No. 16?

When the NFL holds its 51st annual player selections Tuesday, beginning at 8 a.m. at the Marquis Marriott Hotel in Manhattan, New York Giants General Manager George Young predicts: "There's going to be a lot of gamesmanship. People are looking for a two-for-one sale, saying, 'I'll move down if you give me something extra.' People might want to go for quantity instead of quality."

Scouts around the league say that this draft is top-heavy with running backs and offensive linemen and that the teams looking to move up into the elite top four picks likely are doing so to land either of the two highest-regarded quarterbacks -- Purdue's Jim Everett and Iowa's Chuck Long.

Tampa Bay has the No. 1 pick and wants to select Bo Jackson, the Heisman Trophy-winning running back from Auburn. However, the Buccaneers (2-14) haven't been able to sign him. Other NFL teams have called Tampa Bay to offer trade bait; Jackson has talked with Birmingham of the U.S. Football League, the league that has signed the last three Heisman winners. Jackson talks, too, of a baseball career.

Although it is true the Buccaneers already have All-Pro running back James Wilder in their one-back offense, Wilder has touched the ball nearly 1,000 times (running and receiving) over the past three years, enough to send most men to the scrap heap. To avoid quick extinction, Wilder, 27, could use Jackson and perhaps a two-back set.

Of course, these are the same Buccaneers who, with the No. 1 pick in the draft, selected running back Ricky Bell ahead of Tony Dorsett in 1977. One year later, the Buccaneers passed up the right to select fullback Earl Campbell, a future three-time NFL most valuable player, giving away the top pick in a trade with Houston. (They selected quarterback Doug Williams instead.)

The Buccaneers' past bungles with pick numero uno give cause for some uncertainty. Yet club owner Hugh Culverhouse told a press gathering this week: "I have never let money stand in the way of signing a player . . . If the draft was held today and he was not signed, I would still draft Bo Jackson . . . I'd say today our chances are 75-25 against us trading Bo Jackson." (In any case, the Buccaneers ought to make the biggest haul of Draft Day '86 since they possess three of the top 28 picks and four of the top 40.)

The Giants' Young said he doesn't expect the Buccaneers to trade Jackson. "Sometimes the first pick in the draft becomes a political pick or a regional pick. This year's Jackson happens to be a box-office pick and this year the team that has the first pick needs to put people in the seats."

Atlanta has the No. 2 pick and all signs point to the Falcons selecting Tony Casillas, the Oklahoma nose tackle. Although the Falcons could use either of the top quarterbacks in this draft (their quarterbacks are David Archer, Turk Schonert and Bob Holly), they gave up a league-high 452 points last season (28 per game), so they had best get some defensive help fast.

On to pick No. 3, where grand intrigue makes its entrance. Houston has the third choice for the second consecutive year and once again will play the role of the power broker. Indianapolis has the fourth pick, having traded up from No. 6 with New Orleans. It is clear that the Colts want to select one of the quarterbacks, preferably Everett over Long. By trading up to fourth, the Colts seem nearly certain to get one or the other.

Ah, but what will Houston do? The Oilers could use a defensive end, and Alabama's Jon Hand, Oklahoma State's Leslie O'Neal or Syracuse's Tim Green would suit just fine. Yet, the Oilers also could select running back Keith Byars of Ohio State. Byars missed much of his senior season because of a foot injury. He recently had surgery on the foot and has been tested by several NFL teams.

It's unclear if Byars will be ready for the start of the NFL season. Dick Steinberg, the Patriots' personnel director, said: "The surgical procedure is one that's almost always successful. Each team has to make their own judgment on Byars . I still think he'll probably go in the upper part of the first round. If he'd been completely healthy, he's arguably the second-best back in the draft."

Then again, the Oilers might select either Everett or Long with the third pick. Houston's current quarterback, Warren Moon, has produced entirely mundane numbers since descending from Canada for the big, big bucks two seasons ago. The Oilers also have the option to trade down with a team that might want one of the quarterbacks (the Rams, perhaps?) and pick up an extra choice.

By 8:30 a.m. Tuesday, the Colts can stop biting their nails, biding their time and figure out if they made the right move by trading up two spots to No. 4.

The cupboard is stocked with quality offensive linemen: tackles Jim Dombrowski (Virginia), Brian Jozwiak (West Virginia) and Doug Williams (Texas A&M) as well as guards John Rienstra (Temple) and Wil Wolford (Vanderbilt).

The Class of '85 included rare class at receiver (Rice, Al Toon, Eddie Brown), but this year's class has an even more rare depth at running back. Besides Jackson and Byars, you'll find that Florida's Neal Anderson, Louisiana State's Garry James, Southern Methodist's Reggie Dupard and Washington State's Reuben Mayes all will be selected in the top two rounds.