Northern fishing is best drifting Lindyrigs with suckers along the 30' to 35' edges near deep water. 4lb Fire Line makes great leaders and can withstand a lot of abuse from the biggest toothy predator. Small diameter lines and leaders are always a must on Geneva. Only go heavier than 4lb at night. Big fish are notorious for living with and feeding on the oily-skinned Ciscos.
Ciscos live in deep water, often near the bottom edge of the thermocline.
To locate the thermocline, without a thermometer, try turning your depth finder' s sensitivity level to the maximum setting. Go to some deep water. You should notice an area of clutter and noise. This noise is generated from all the little bait fish and micro-thingies that live at the thermocline. Fish where structure meets the thermocline.