O Kay guys, I finally got back to doing some fishing after many years. And now I have a few questions. The first topic I would like to have information on is Leaders. I do mainly Bass, Crappie and Catfishing, and would like to know the purpose of using leaders and if they are helpful with any of the types of fishing that I do.So if anyone can guide me to some literature that they believe to be helpful with this subject please let me know.

Thanks
WISHFISHER

In most cases when I use a leader is because I'm looking for a stronger or stiffer line that is more bite resistant. On the opposite end is where I'm using braid and then want to use a mono or floro leader for a more stealthy approach.

normally with  the species your fishing  bass crappie and catfish  i would only use a leader for presentation
say a liter line then the main line for  stealth  or better movement of the lure ,  to float something  off the bottom  as in a Carolina rig .

the  main purpose of using a leader  is either to prevent bite offs ,to act as a shock absorber ,to provide stealth  from the main line . or  for presentation purpose.
or a combination there of.  
for example your main line is braid  or heavier line  but the fishing  situation requires more stealth so you  add a section of  6 lb fluorocarbon  or mono  line to the main line .

 a mono leaders  will stretch  =  stealth  ,shock  absorption, and presentation .

musky and pike may  bite off your lures  so you may want to add a wire leader or heavy fluorocarbon leader.