My favorite technique in the early pre-spawn period is vertical jigging. Tip a 1/4- to 3/8-ounce short-shank jig with a 2- to 3-inch minnow, then drop it to the bottom and hop it along as the boat drifts downstream. Actually, there's a little more to it, especially if there's any kind of wind, which affects the speed of the drift relative to the current. The idea is to keep your line as vertical as possible. That means you'll have to drift at exactly the same speed as the current. With an upriver wind, use the trolling motor to pull the boat downstream; with a downriver wind, pull it upstream. Keep adjusting boat speed until the line stays vertical. This way, you'll be able to detect even the lightest strike.