I always sweep my rod forward when it loads up from a fish while I'm reeling to make sure I get the fish on top. Not really a hook set but it helps get the fish's head up and any trace of slack out of the line. Reeling should be reasonably fast until the crappie pops to the top then steady to the boat. Sometimes the fish are just going to come off. I see lots of clients reel way too fast and get the crappie tumbling. The majority of the time that fish will come off. If there is a medium to heavy chop on the water you have to be even more aware of how fast you are reeling. Lots of folks get excited the closer the fish gets to the boat and they unwittingly pull the hooks loose. I had a client do that on a big largemouth bass (green carp) yesterday.