There are no hard and fast rules that cover every situation. Line depends on what you are fishing for, water clarity, and the structure and cover or lack thereof that you are fishing. For crappie fishing LOZ and Truman I use 4# diam/15# test powerpro braid. For trolling crappie on Stockton I use 10# fluoro. About all I use mono on are my topwater stick or an ultralight for clear water crappie. The rest of my bass rods get either 10, 15, 20, or 25 pound abrazX fluoro. Flipping heavy cover brings out the 25#. Brushpiles and coontail fishing on a stained body of water usually gets 20#. real clear water fishing football jig gets 15 as does cranking a squarebill in heavy cover. I use 10 pound on my stickbait rod and cranking rod (clear water).