Some ice-fishing book that we liked are:
Ice fishing : a complete guide, basic to advanced / by Jim Capossela
Modern methods of ice fishing / by Tom Gruenwald
Hooked on ice fishing / by Tom Gruenwald
Hooked on ice fishing II : panfish / by Tom Gruenwald
Hooked on ice fishing III : gamefish / by Tom Gruenwald
1. Keeping some slush in the hole may improve your success because it blocks some of the light that might enter through the hole.
2. If your trying to find a drop off or just some fish, you can do it without drilling a hole all the way through the ice. Here’s how you can do it: Drill a hole about 2-3 inches into the ice and fill it with water. Put your transducer in the partly drilled hole and you can see the structure on your screen. Although the depth won’t be exact you can still find drop offs etc.