I'm certainly not as good as most of the crappie fishin folks here, but I can tell you what works for me.
The drop offs near structure are key to me. I try to set up in 20-25' of water. I use one submersible white light (Q-beam) and one lantern to light the boat. I hang it up and out over the water on a homemade hanger. If there is anyone else fishing with me, I'll use two Q-beams and the lantern. This would vary according to the boat you are using, I think. I'm using a small jon boat!
I usually don't get the fish biting right away, it takes an hour or two before I can start really judging how the night is going to go, and then it has to be truly dark not just "dusk". I use minnows only, because that is all I know how to use.
Anchoring at night is real important. You need to be as stationary as possible. I work hard to start with to make sure my anchors are set good. I use one in front and one in back to keep from getting any sway. Set em good before you start fishing. You'll save yourself a headache later.
From reading your post, I see where two things are possible. Either the fish are not feeding at the time you are there, OR you haven't got the depth right yet.
The depth of the bite, I've found, is sometimes NOT relavent to anything on your fishfinder! I'm very sure that there are many that will dissagree with me on that, but it is what works for me. I will usually start deep (just a crank or two off the bottom) in the heat of the summer or the cold of the winter. I'll also fish in deeper water then, sometimes. I'll work up a foot or so at a time until I start getting bit. In the spring and fall, I start about 12' down and work it up a foot or so at a time from there til I get bit. This works almost all the time for me. There are the occasion when I'll have to go deeper in the spring and fall, and that is just part of finding the right depth.
Finding the depth of the bite is as important as bringing your bait!
Not many people use the stuff I do, but I usually take me a couple 12' telescopic poles in the spring/fall. I set the bobber for the depth I want and find it very easy to manage. I also use the lightweight spinning set ups to tightline. Some nights the fish will ONLY want one or the other!
It's a constant adjustment...one thing at a time. I'm certainly no expert, but I promise you I bring my share home.
Good luck!
"Be Ye Fishers of Men" You catch them- He will clean them