Fish4thepeck gives some SAGE advice, however he uses a bait I've not ever used. I have stood next to people who have used that in rivers/moving water and done VERY well, actually - can't wait to try that myself. Tipping with a minnow will dang near quadruple your chances in my opinion.
Time - Anytime right before or at first light and after dark and usually up until 10pm. in my experience. They can feed for 20 min or can go for four hours. But dusk and dawn are best for numbers. An hour before and and hour after, of course.
What - Leeches are best, but you cannot find them in ANY bait store in TN I'm pretty sure. Minnows and crawlers are their other favorite foods. Put it on the bottom as he said and lift about 1 reel, just to get the weight off the bottom. Verticle is the way to go, especially this time of year. You can jig vertically using a jig head or plain #4 hook, working the minnow VERY slow, or slip cork to the depth of 6in above the bottom when fortunate enough to still fish these finicky dudes. You'll find your best days will be when there is a "walleye chop" of a slow chop on top from wind. Overcast/cloudy day.
If you use the simple method of a pinch on 1/8 weight and then let the snell (length of line between hook and sinker) with a bare hook to float along behind the weight. You are going to catch sauger/walleye and many other species. Most around here that I have fished with use about 12 to 14 inches. I've used up to a 9ft snell on long line trolls, it allows the "flow" effect work for you. Bottom bouncers or Lindy Rig's are made for this tactic. That is the real trick. To get your minnow horizontal to the bottom within 6 inches. Much like a small Carolina Rig setup. Hanging directly in their strike zone. I've seen them move through areas on an aqua view and have never seen one sit/stand verticle. Though that would be cool to see. They swim in like a swarm of ants when they pack up and feed. But also can be sitting there on all the types of structures. The point is to work slow, off the bottom, and sliding your hand right and left to get that minnow to laydown. Hand feed 'em. You'll go mad at first. You'll go a few times and not see a one. Then other times, you can't get them not to bite. Work it. Traditional points, breaks, eddys, and structure hold fish. I've had luck in the early spring through the middle summer months using a shadrap, shad color. Minnows my man. Learn to love them if you want to catch sauger/walleye.
When - I've fished them 12 mos. Not many in the summer here, but it's increasing, I'll tell you when they've peaked. They are everywhere. Just got to find them like the other fishes.
Just as Bent Rod, he caught one in the middle of a whole school of crappies!
And he as well as others, use the drop shot from time to time. Don't be afraid. Just don't thumb it.