Found this webist with a few good tips
Inline Weights are used as a depth control device for trolling live bait. The most common application is open water trolling with crawler harnesses for walleye on the Great Lakes. Walleye 101 and Walleye Kid have lots of great information and videos to help you use Inline Weights to catch more fish.
What: great tool for depth control while fishing crawler harnesses for walleye
Depth: used to target fish at a variety of depths by changing size of the weight, length of line, and speed
Baits: work best for crawler harnesses but can be used for spoons and single hook minnow rigs
Leader /Line: best leader is 5-7 longer causes fish netting issues. Mainline of 12-14 lbs is best.
Speed: effective at speeds from 0.6 to 1.6 MPH. Inline weights are highly speed dependent and even a small change in speed can have a significant impact on how deep your lure is running
Rod & Reel: line counter trolling combos produce the best results. Success requires experimenting with the amount of line let out and being able to repeat a distance once you catch a fish.
Sizes: wide range of sizes including weights from ½ oz to 3 ounces. The most common are 1oz and 2oz.
Colors: the majority of inline weights are plain unpainted lead. Colored fish shapes are also available
Cost: they range in price from $1.00 -$2.50 each depending on size, type, quality, and where you purchase them. Unpainted, beaded chain inline weights are generally the best overall value and quality.
Setup: use a crank bait snap on your main line. Ball bearing or crane swivel on the harness to avoid twists.
Rule of Thumb: this one is a little tricky. At a speed of 1.3 MPH a one-ounce inline weight might run one foot down for every three feet back. At a speed of 0.8 MPH a one-ounce inline weight might run one foot down for every two feet back. One-ounce weights are more speed dependent than heavier weights.
Getting Set Up on the Water
Step One: look for an area with fish at a variety of depths in the water column. You will probably have better success with inline weights if you can find active fish in the middle of the water column.
Step Two: determine which fish you plan to target and the speed you will be trolling. For example: fish on your sonar are 20 feet down over 40 feet of water and you will start trolling at 1.3 MPH.
Step Three: select the right inline weight and distance. To target fish 20 feet down select a one-ounce inline weight and run it 50 feet back at 1.3 MPH. This will put it 15-18 feet down and in the strike zone. Run your other lines 45, 55, and 60 feet back. Hook them up to a planner boards and hang on.
Step Four: Change one variable next speed. Go slightly faster or slightly slower to move you baits up and down in the water column and to see if a different speed triggers fish. Adjust as you find success.
1. Trying to manage too many variables. Use all the same weights and vary length of line and speed.
2. Fishing below the fish. Walleye will come up a long way to hit a lure, they wont go down to feed
3. Worrying about color. Get the lures above the fish at the right speed then manage the color variable