I don't know if your 6-cyl has them or not, but before you slam the hood, I'd suggest you look for / check for the condition of the belt tensioner. Make sure the tensioner still has good 'spring' left in it. Most have an indicator arrow on them to indicate the proper 'range' of tension for the serpentine belt.
Also look at the other pulleys in the system; the alternator, the water pump, an idler (if the system has one). Give them all a good spin by hand. Listen for any noise and feel for any roughness in their operation. While you have the belt off, it is the best time to give all of these pulleys a simple inspection. These pulleys don't last forever either....
Oh yeah, if you have a clutched fan, give it a spin too. My fan clutch started making all kinds of noise that I thought my water pump was going away; come to find out it was my fan clutch.
-- '95 YJ, 4-cyl, 5-speed.
From Dec-Mar, it wears an 80" snowplow. From Apr-Nov, it gets muddy on the 2-tracks!
"War does not determine who is right, war determines who is left."