Another simple question whose answer again starts with, “It depends….” A nine-foot leader is fairly standard and a good starting point when fishing a floating or intermediate line. When fishing deeper with a sinking line I prefer a much shorter leader to help get the fly down to the fish. A three-foot leader might get you kicked off a spring creek, but it can be very effective in the striper game. Current speed and water clarity may influence the leader length on sinking-line rigs. As the season progresses, the bigger bass can get timid. When sight-casting in calm, clear water I’ll often lengthen a leader out to 12 feet and keep dropping the size of the tippet until the fish will eat. Sunny August days may call for a six-weight line rigged with a 12-foot leader with six lb test tippet. I tie all of my leaders with fluorocarbon, but that’s a topic for another day.
"I need to replace the mono on one of my spinning rods. I remember fishing with a different kind of line on our charter last season. What were we using?"
A number of my rods are always rigged with braided line. It is much stronger for a given diameter than mono and will produce less drag in current at the same pound test. Unlike monofilament it has almost no memory, adding distance to your casts. It doesn't stretch, so you can feel every tap, bump and bite. Braided line does have drawbacks and needs to be rigged differently than mono. I fish Superbraid, FireLine and Power Braid.
Look for an upcoming article with more details and suggestions about rigging and fishing braided line.