when i tune i rig it just like i am going to fish it. proper weight, leader length, & trolling speed. then i let it out as far back as possible until i can just see it working in the water. if it tends to pull to the left, bend the eye to the right. vice versa for the other way. just tweak it in very small amounts, it doesnt seem to take much. you might have to keep tweaking and checking until you get it right. i also give it a quick check after i have caught a fish to make sure its still good.
hope this helps you.