Can the clutch only cause slipping or are there other problems that can be associated with the clutch? For example, not getting it into gear?

 

bad pressure plate, clutch springs, pilot bearing would make shifting hard or not possible.release bearing would make the infamous helicopter noise.
glazed clutch disk or flywheel could cause clutch chatter.
thats all i can think for now.

 

Like he said there are several things to go wrong with a clutch, each has different symptoms. My LS was recently refusing to go into any gear unless at a near complete stop, and making clicking sounds when it did. I suspected it was the throwout bearing and sure enough when I got it apart the bearing was in 3 pieces, the disc was fine however looked like it had thousands more miles to go. I replaced everything however.