New on the tube

First Years Airs: 8 p.m., NBC (Channel 41) Stars: Samantha Mathis, Mackenzie Astin, Sydney Tamiia Poitier, James Roday, Ken Marino, Eric Schaeffer In brief: Five first-year lawyers share the same office and the same house! But is it any good? This show with a simple premise starts confidently in midstream, but viewers will catch up to it in no time. Spare, brisk writing moves the story along, and most importantly, I found myself caring about one or two of the characters. (Considering that they're lawyer-yuppies who can afford a big house in San Francisco, that's saying something.) If the show has a breakout star, it'll be Sidney Poitier's daughter. Is it a survivor? Mondays have not been kind to NBC, although the network seems to excel in lawyer shows ("Ed," the "Law & Orders"). To succeed against "Ally McBeal," "First Years" will have to dial down the sexual interplay and tell compelling legal stories like the ones in tonight's episode. >>>