the clutch is starting to slip on my roommates car and its a 97 jetta 2.0L wiht a cable operated clutch. does anyone know how to adjust it so i can get a bit more life out of it?

Greyhare is around here someweres..he may cue in
I sell clutches all day long at work, i can tell you, that adjusting the cable MAY not fix the problem, if the clutch is slipping under load, your pressure plate and clutch plate is worn down, infact, once removed from the car, id be willing to bed the face of the clutch (if its organic) is glazed, and the pressure plate has a few blue streaks in it.

I'll tell Greyhare to pop in here when I see him at lunch.

Most likely it is a self adjusting cable. The manual adjust cables were used on the 1st and 2nd gen cars, '97 is 3rd gen.

Matt is correct the clutch is most likly just worn out.

Here is a good place for parts, I can list others if needed.

http://www.gprparts.com/

They have a complete clutch kit with the recomended replacement parts. I would recomend the Sachs with the dampened disk. (Origional factory for the car)
Replacing the clutch cable is not required but is a good idea.

Will the work be done at a shop or home? I have lost count of how many I have done and can give pointers that will save a lot of pain.

i may be doing it for him in shop.

Get the shop manual from Bentley publishers. It is a bit expensive but there is none better for the VW. Most dealers have and use them.