This is probably one of the most recognizable lure's, and its been around for over a century. They're just as good now as they were then! The basic spinnie will be good for smallmouth, trout and more.
This is a pretty simple spoon to use: use a snap to attach it so it can move around freely. Don't bring it in with a study retrieve, but instead use rod-tip twitches to create more erratic motion to make it more interesting for the fish you're trying to reel in. Often the fish will strike when the lure drops, so I prefer to use the drop-and-flutter.
At a deeper drop-off, I have had luck jigging a spoon up and down, where, again the strike occurs on the downward motion.