Each year is different, but normally sometime around the middle of June we start switching from jigs and minnows to crawler bait or leeches. My best luck with crawlers varies from just a plain hook and bead with anywhere from a 3' to 6' leader fished behind a bottom bouncer. As the summer bite progresses I start adding spinners to the presentation. I tie my own spinner baits and use barrel floats instead of the normal string of 5 or 6 beads. I also like to use Indiana blades as they will spin with slower presentations.
Some fishermen like to use the multiple hook worm harness.
Personally I like using a single hook. If I am getting short bites I start breaking the night crawlers in half. Using a short piece of crawler has worked quite well with the floating baits. Summer live bait presentations of leeches and crawlers usually require when you first feel the bite to feed a bit of line out to the fish before setting the hook. It is a transition from the cold water presentation of jigging that when you sense the slightest hesitation to set the hook.