To add to the two above. Let me say that pre-spawn occurs when the water temps reach up into the mid 50's to low 60's. Once the waters hit somewhere around 62, (give or take a few degrees) the fish move up. Normally the first fish to move up seem to be of the larger class(females). The males start looking for hard bottom areas and timber so they can make a nest. Now, all fish do not spawn at the same time, some spawn earlier, others later.
Now during this time when the waters hit the mid 50's the fish do go on the feed. Look for deeper water areas, creek beds, drop offs (could be as small as a 1-2ft ledge), these are area's the fish wil move up looking for an easy meal. Like stated, spinnerbaits, cranks, jerkbaits, worms, a-rigs will all produce these stagged fish once you locate them.
Now, for some strange reason the fish move up onto beds somewhere around the full moon phases and only stay for a short time. They move in waves and fish may spawn in most areas of the country from early March to mid June. Some just are late spawners. Once they are up looking to spawn site fishing can be productive if you can get past the male who is much more aggressive then the female. If you get her fired up then you probably can catch her. But it's hard to get past the male. Jerkbaits, wakebaits, and plastics all work wonders as will a frog or swimbait. Remember these fish aren't trying to eat, the just don't want it where they are. Once the fish finish spawning, the males stay with the fry for a bit to guard them while the females return to deeper areas to regroup and feed. If you see bluegill beds, these are great areas to target these fish as they feed up to regain their strengh.
Normally if there are fish on beds there are fish out past them as well in the pre-spawn mood if you can locate them. During certain times you will have all three, pre-spawn, spawning, and post-spawn fish. Don't just try and fish for the ones you can see, you will be missing a lot of fish just outside them that are willing to feed and can be caught much easier then the ones that have only spawning on their minds.