The angler pursuing these fish needs to use small hooks, the smallest float possible, and pay strict attention. Bluegills and sunfish will suspend at any depth between the surface and the bottom, and ordinarily will not move much to take a bait, so proper depth setting is critical. Watch carefully for those bites on the drop, and set your depth accordingly. An exception to this cautious behavior is the spawn, when male bluegills and sunfish will vigorously attack anything coming near their nests. Most of the above applies to crappies, with the exceptions that they tend to seek out deeper water, are usually found below the level of light penetration, and feed primarily on minnows.
Crappies have a well documented fondness for solid, complex structure like brushpiles.
If your lake has brushpiles, that's where you'll find the crappies. During early spring, bluegills, sunfish, and crappies all have an uncanny knack for finding the warmest water in the lake. Huge schools of them will occupy small warm water pockets. This works to your advantage - not only are they feeding heavily, but competition dictates that they must abandon their usual caution. Find the warm water and you will have some fantastic fishing.