How do you know if you're running a spinnerbait, swimbait or any other lure at the correct depth for suspended fish?

As an ambush predator, bass will strike from below. If you have determined the fish are indeed suspended, you can choose a weighted bait which drops or runs to a depth anywhere above the fish. I wouldn't worry as much about finding the right depth as much as I'd worry about getting a good action with the bait which would be attractive to the fish below. Try different approaches and vary your retrieve speed until you get bit. Or, you could just rig up a senko and drop it in on the fish. Its fluttering fall has enticed many a bass.

Whets

8-)

I would disagree and say depth is one of the most important things you should consider.

For baits that sink (spinnerbaits, swim baits, etc.) grab a 5 gallon bucket and fill it with one foot of water. Grab a stop watch and drop the lure, note how long it takes to hit the bottom, and do this for each one you are interested in. When you get to the water you will know how long it takes it for the bait to fall each foot.

Practice reeling the bait on the water in a place where you can see it to determine the speed required to keep it running at one depth. When you got it figured out, cast and count it to the depth you want, then reel at the right speed to keep it there.

For crank baits, I use my electronics.  I will throw baits/move deeper until I can no longer dig them in the bottom. When I lose touch, I note the depth.

I would think depth is very important too. I was watching Bill Dance, and he stated the three key words for bass fishing are: Location, Depth, and Presentation. This is what led me to my question.

I'm definitely going to do what you suggested. Those were some very good ideas. I don't have an area to throw and watch the bait swim up, but I'll figure something out. I don't have electronics or a topo map for my small lake, but I can make my own rough sketch by using your method.