The North American Soccer League begins the second part of its season tonight as 12 teams vie in the playoffs for a trip to Soccer Bowl '77 in Portland, Aug. 28.

The league, which just concluded its 10th year and drew well over 3 million fans, has a new wrinkle in its playoff system that is designed to increase competition and fan enjoyment and fatten team owners' pocketbooks.

The top three teams in each of the four divisions are in the playoffs. The second-place team hosts the third-place finisher and the winner of that contest plays the division titlist in a two-game, home-and-home series. If the teams split, an overtime period and, if necessary, a shootout is held immediately following the second game.

The Northern Division winnner then mees the Eastern Division survivor for the Atlantic Conference crown, also in a home-and-home series. The Western winner plays the Southern winner for the Pacific Conference title. The two survivors then meet for the NASL title.

Here is a look at the participants. ATLANTIC CONFERENCE Eastern Division

This looks like The Cosmos' year. Despite a 15-11 record, the second-place Cosmos are a good bet to whip thirdplace Tampa Bay (15-12, 131 points) at Giant Stadium tonight and go on to topple the division winner, Ford Lauderdal (19-7, 161). The superstar lineup of Pele, franz Beckenbauer and Giorgio Chinaglia helped the Cosmos score 60 goals, second only toLos Angeles. Also the NASL leader in attendance (34, 142 average). The Cosmos have won six straight games at home and captured three of the four games against tampa Bay and Fort Lauderdale this season.

Tampa Bay limped into the playoffs, winning only four of its last seven games. Eddy Firmani quit suddenly as coach and shortly afterward took over the reins of the somewhat disorganized Cosmos. The Rowdies, also with bona fide superstars - Rodney Marsh (27 points), Derek Smethurst (42 points) and goalie Paul Hammond - seemed to lose their flash, not to mention many games, after Firmani's exit.

Fort Lauderdale has been the league's surprise. Only 6-18 last season as the Miami Toros, the Strikers registered the best won-loss mark in the league. Goalkeeper Gordan Banks, the 37-year-old wonder who is a strong candidate for MVP, and a no-name defense limited opponents to only 29 goals, the best in the NASL.

Prediction - Cosmos. NOrthern Division

The oly reason three clubs from this totoriously weak divisions are competing in the playoffs is because league rules demand it.

Toronto, the defending NASL champion, emerged as the division are competing in the playoffs is because as the division are completing in the division winner with a 13-13 record and 115 points. As was the case last year, Toronto's offense is its defense and it should have no trouble knockings off St. LOuis and Rochester to earn spot in the semifinals.

Prediction: Toronto. Pacific Conference Western Division The Minnesota Kicks (16.10, 137), division winners, dropped their final two games of the regular season, but with the help of the league's second-highest attendance (32,771) should be able to rekindle their early-season fire.

The Vancouver Whitecaps (14.12,124) needed a final 2-0 victory over Portland to edge the Seatle Sounders (14-12, 123) for second place and the home-field advantage in their first-round game. Neither Vancouver, surrendering 46 goals, nor Seattle, 44, have shown it has the defense to handle Minnesota. The Vancouver-Scattle game can be rated a tossup.

Prediction: Minnesota. Southern Division

Both Southern Division champion Dallas (18-8, 161), and runner-up Los Angeles (15-11, 147) are hurting , Los Angeles, which hosts San Jose (14-12,119) in a first-round game, is the highest-scoring team in the NASL, but the Aztees will be missing forward Steve David, who led the league in scoring (53 points), because of a knee operation.

Dallas may be without the services of striker Kyle Rote Jr., 28 points, who also has knee problems. The Tornado will have to rely on the league's foruth-best defense (37 goals allowed), anchored by the NASL leading goalie Kenny Cooper.

San Jose is dangerous with Paul Childs, Leroy DeLeon and Illija Miticup front. (KEY OFF) rediction: (KEYWORD) Dallas.