Fall time is one of the best times of the year to chase after big bluegills. Usually the 'gills will migrate from their deeper water haunts back toward the shoreline. There they will hold in some sort of cover like brush piles or green weeds. I have found that fly fishing with a woolybugger in either black or olive color seems to work pretty well. There will also be some good top water action in the mornings and evenings. That is when the poppers, sponge bugs and other dry flies can be your best bet. I tried something new last fall with great success. I used a slip float with a small jig baited with Berkley Gulp Alive 1" fish fry.
Good luck
Andrew