By predicting the Dallas Cowboys will win 12 games this season, Coach Tom Landry extended his blessing today to what he considers the positive effects from a tough and more regimented training camp.

In almost the same breath, though, Landry said the Washington Redskins should be the favorites to repeat as NFC champions this season. Dallas and Washington begin the regular season Monday night at RFK Stadium.

"You still have to favor the team that won it last year," he said. "And I can tell that Washington played very good defense in the preseason. Actually, though, it was the kicking game that won it for them last year. So that's the area where they need to continue to excel."

The Cowboys have lost three straight NFC championship games and that albatross is getting heavier. In Dallas, they are being referred to again as "Next Year's Champions." If Washington does repeat as the NFC representative to the Super Bowl, more doubts will be raised about a team that is growing old and coaching methods that are brand-new with Landry.

One ray of hope with Dallas is that teams that won the NFC title in 1980 and '81--Philadelphia and San Francisco--did not even return to the playoffs the following season.

Will Washington be another one-shot champion? "Washington was not the most talented team in the NFC last season," Landry said. "They just got hot and they were hard to catch. Yes, it's going to be hard to recreate that. But they have two good things going for them. They've got a good coach and a good team morale. And those things will take you a long way."

After an intense training camp that included stricter curfews and a new emphasis on the psychological aspects, the Cowboys will soon learn whether the regimen of Fort Landry worked. Although the defense continues to lag, Landry said most of the Cowboys' muscle was flexed during the exhibition season.

Landry spent much of the summer pondering what he calls the "missing ingredient," an intangible that kept Dallas out of the Super Bowl. While refusing to define the ingredient, Landry indicated today it might have been found during the preseason.

"Realistically, I think we can win 12 games this season," he said. "We achieved most of our goals, at least the ones we set. Defensively, the pass rush still has to improve, but we've got some time for it to improve. But if the defensive secondary continues to play that well, we're going to win a few games."

Landry said he dreads the thought of beginning the season at RFK Stadium. Today, the hype and hoopla that normally surrounds the game began when Washington fullback John Riggins said the Cowboys no longer belong to the NFL's elite.

Wide receiver Butch Johnson responded angrily to Riggins' charge that Dallas thrives merely on its mystique. "Put them in New Orleans' uniforms and they might not win many games," Riggins said. Responded Johnson. "I tend to wonder what uniform Riggins wears. Because after the championship game last season he didn't even have enough class to show up for the team's pep rally."

Cornerback Dennis Thurman, who normally is outspoken, had a more reserved attitude. "Any time you are the champions, you can do all the talking you want," he said.

He added, "Washington had better remember that this is a new day and the entire nation might see them go down Monday night." Cowboys players generally like to play at RFK Stadium, which has the loudest and most spirited fans they contend with all season.

Quarterback Danny White, who remembers nothing from the NFC title game after being knocked unconscious by Dexter Manley, said he preferred the Washington crowd. "They're loud, but they can get quiet pretty quick. In fact, it can be one of the quietest places to play when things aren't going too well . . . "