In my opinion, the right depth is the most important thing. If your marking fish but not getting a takedown, try adjusting your depth first. Also try more pronounced "s" turns (if your useing a short set-back). This will not only change your lures action, but also it's speed and depth. If you start getting hits on the inside of turns slow down, outside turns speed up a bit. I have found that color is very important, but don't overlook lure action also.
I have experienced fishing with the exact same set-ups on each side of the boat, same lure design, color, dodger, leader length, depth, scent, speed, the only difference was the action between the two lures. One was a hot spot apex, the other a pro-troll kok killer. They hammered the kok killer lure that day, wouldn't touch the apex...the only difference was the action between the two that they seemed to prefer that day. One mph slower or faster and it might have been the other way around.
There are definite colors they like through out the day, and always keep in mind as the day progresses you not only need to adjust your depth, but also your colors for that depth as you go down the water column. I take a few batches of corn, and always have one batch dyed pink. Some days they will prefer one over the other.
There are also days when your most consistent lure goes cold, so don't hesitate to try something totally different....don't keep dragging something around just because it worked the day before, sometimes koks like to play games with us! Oh, I almost forgot...adjust your set-back also if your not getting fish. There are times a short set-back works with ball trolls, but if that's not working try shedding the trolls, or get back farther in back of the boat. One more option you have that I haven't seen mentioned is change your direction in relation to where the sun is. If the sun is over head there's not much you can do, but early and late in the day try not to troll into the sun, more hits will occur going either perpendicular or away.
