Crappie bite where you find them. Obviously ya gotta find them before you can catch them. The smaller the water, usually the easier it is - but sonar is an absolute must when you have no idea what's on bottom or how deep.
Want crappie or any other pan fish? Fish a lake.
My friend and I have been fishing a decent size lake recently for the first time and after three trips are still learning key structure areas and depths. (By structure I mean for example humps out from shore; points that extend way out that may even be perpendicular to a straight shore line; narrowed areas where the two shores are closer than any other and have some depth (over 4') and hopefully weeds ; weed bed edges - especially those away from shore; coves - rounded indentations or corners in a lake that adjacent to deeper water and weeds; steep shore lines or flats that drop off fast to a flat shelf).
Crappie in one lake can be found over or in many structure types (see above) on the same day. Granted, 3 or more fish may be in one area, but schools are common numbering over 15 or more catchable fish. Catch one and the schoolies turn on like a conveyor belt.
As far as lures go, can't beat a jig and soft plastic for the search, find and catch. Depending on the size of the water and the largest average size the crappies run, 1/16 and 1/8 oz ball head jigs (unpainted) suffice for all depths and speeds of retrieve - usually a slooow and uneven retrieve. We used jigs under floats this weekend and caught many crappie near shore and deeper for an hour.
Vertical jigging in 8' or more is a nice way to get bit when the fish are cooperative.
Minnow imitations with flat (not curl) tail seem to do well regardless of presentation.
We fished from a small boat using only a trolling motor and did quite well - even when the wind picked up. The important thing to remember is that the lure is the search tool along with sonar and once fish are found (regardless of mixed species), anchor and cast all around the boat to find the school if it exists. I may occupy a rectangle only 10-20 yd. wide or you may be near the middle of one in a cove (happened to me today - I caught fish shallow and in open water that was deeper.)
Always be aware of any surface activity - splashes or and surface disruption - an always cast to it.
Line size - stay with 6 or less pound test leader or main line. Fish are not line shy, but ignore a lure that doesn't act right on heavier line. You may get a away with 8#, but be safe and go lighter.
A bit much to absorb, but the above applies to most freshwater species of fish caught. In fact if I caught crappie in an area, there would also be a high probability of catching sunnies, yellow perch, bass and pickerel - and on same lure.
Know the bottom! I can't emphasize that enough. But also remember it for future reference.