Here are a couple links to some wintertime tips. In the fall find the baitfish and you will usually find Crappie following. October tends to be a great month for Crappie fishing. I have found the to move shallow to warmer waters before they head off to deep waters for the winter. I would think you should find them suspended on the dock pilings. I would try each piling individually and watch your depths so you will know where you find them as they tend to school up in the spring and fall. Hopefully this helps and you can find some more info on the web.
How to Catch Big Bluegills with Jigs and Plastics - Wired2Fish.com
How to Catch Big Bluegills with Jigs and Plastics - Wired2Fish.com