Like bugs said it all about trial and error. If you wouldn't mind spending 30 bucks you can buy the precision trolling guide. It has all the dive curves for most of the lures on the market. They have taken the time and figured all out for you. It tells you the line out you need and speed to get the lure down at certian depths.
http://www.basspro.com/servlet/catal...rTarget=browse
Ted
Neither snow nor rain nor heat nor gloom of night will keep me from crappie fishing!
2010 Lake of the Ozarks Super Slab Champion