I'd set up with he same size line & jigheads on all my rods. Try to set all your rod tips about an even distance from the water. Pick a spot on your lake that has a gradual taper towards shallow water (preferrably snag free). Start in the deeper water and get your speed set and all your rods casted out to approx. the same distance (a long throw works for me). As you are trolling to the shallow water (a good starting point would be .8 - 1.0 mph) watch your rod tips until you see them bouncing as your jigs begin dragging bottom. Check your depth and you'll know how deep theyre running.

Do this again with only a half cast....switch jighead weights and do it again...short cast again...adding a splitshot...again...again...

I hope you get the picture on how we know approx how deep our jigs are running. These experiments wont take that long and the info gained is invaluable for you as a longliner IMO. Nobody can tell you how deep the jigs off your boat will run as everybody set's their boats up differently. Next, watch your graph and go find some fish. Preferred locations for me is water 20' deep or less as I can get my jigs down there for the fish to see if need be but I havent really tried catching fish in water any deeper than that. Remember to run your jigs a couple feet ABOVE the fish and the agressive fish should take your offerings. If not then dont waste a whole afternoon...go find some more fish and hopefully they'll bite.

Fish will hit the tube and split tail jigs as I fish a good many tied jigs from time to time. I do prefer slider and curly tail grubs as the main jigs in my spread as there's more aggressive movement to the jig which IMO aggrevates the fish into biting.You'll want several different colors as you never know from day to day (sometimes hour to hour) on which color works the best.

Just a precaution though...longlining is very addictive. Once you get used to covering so much water in a day's fishing trip it will become VERY HARD to slow back down and fish any other way. And...longlining put as many (if not more) fish in the boat as any other method of fishing. Good luck with your fishing.