YOU GOTTA LAUGH WHEN YOU'RE AT `30 ROCK'.

Byline: David Kronke Television Critic

Life is pretty good for the tartly sardonic Liz Lemon (Tina Fey):

She's head writer on NBC's successful sketch-comedy series ``The Girlie Show'' and likes her cast and colleagues. So, naturally, this cannot last, and sure enough, it's mere minutes into tonight's premiere of ``30 Rock'' that Liz is plagued by Jack Donaghy (Alec Baldwin), an arrogant, meddling executive for ``NBC-GE-Universal-Kmart.''

Jack insists on changes on the show -- ``You take things that are already working and you fix them,'' Liz summarizes incredulously.

``Sometimes you have to change things that are perfectly good just to make them your own,'' Jack rejoins. Namely, he wants to bring in Tracy Jordan (Tracy Morgan), a neurotic movie star -- any resemblance to Martin Lawrence is purely not actionable enough -- Jack happened to have met once.

Liz takes a meeting with Jordan, which naturally winds up in a strip club, placing her desperately close to missing the broadcast of her live show.

It's hard to see why ``The Girlie Show'' is such a hit, because what little we see of it looks awfully lame: Its jittery star (Jane Krakowski of ``Ally McBeal'') even seems to understand that she's not very good in certain sketches.

``30 Rock'' itself is better, though uneven. Next week's episode has some funny moments when ``The Girlie Show'' undergoes an extreme makeover and Liz and Tracy throw a lavish party after they hack off the entire cast and crew, though how Liz alienates her staff is a bit contrived: One would imagine a TV professional would understand there are live monitors on her set.

Still, Baldwin is very funny as a self-assured oaf who promises devastation for anything in his path, and Fey is appealing as the headstrong yet harried Liz. NBC's similar ``Studio 60 on the Sunset Strip'' is more sharply written and performed, and there's little that suggests many viewers are that interested in the workings behind TV shows. But Fey's attitude seems to be, if life gives you Liz Lemon, forget lemonade: Make ``30 Rock.''

David Kronke, [phone]

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30 ROCK - Three stars

What: ``Saturday Night Live'' alumna Tina Fey's comedy looking behind the scenes at a ``Saturday Night Live''-style TV show. Hey, write what you know.

Where: NBC (Channel 4).

When: 8 tonight.

In a nutshell: Uneven, though Fey as the show's head writer and Alec Baldwin as a pompous network executive are very funny.

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Photo:

Alec Baldwin, left, Tina Fey and Tracy Morgan are the behind-the-scenes players in a ``Saturday Night Live''-style sketch comedy show on NBC's new ``30 Rock,'' debuting tonight.