I learnt useful "beginner's stuff" from my extremely well-written Behringer Composer manual:
Helped me understand and actually HEAR the nature of comp and limiting...
Helped me not F up my quasi-mastering for my demos....
Helped me get a deal because my demo was "louder than anyone else's"
slow attack /slow release/low thresh/low ratio= leveling for program material
High thresh/high ratio/fast attack/slow release = program limiting.
BUT these settings vary from plug-in to plug-in/hardware to hardware;
Classic engineer's answer: "It depends"