In your introduction, clearly identify your subject--in this case, the group you are classifying. If you have narrowed your subject in any way (for example, types of bad drivers, rock guitarists, orannoying moviegoers), you should make this clear from the start.
In your introduction, you may also want to provide some specific descriptive or informative details to attract the interest of your readers and suggest the purpose of the essay.
Finally, be sure to include a thesis sentence (usually at the end of the introduction) that briefly identifies the main types or approaches you are about to examine.
Here's an example of a short but effective introductory ...view middle of the document...
Just make sure that the order of your body paragraphs matches the arrangement promised in your thesis sentence.
Here, in the body of the essay on baseball fans, you can see that the writer has fulfilled the expectations set up in the introduction. (In each body paragraph, the topic sentence is in italics.)
The Party Rooter goes to games for the hot dogs, the gimmicks, the giveaways, and the companionship; he's not really that interested in the ballgame itself. The Party Rooter is the sort of fan who shows up on Buck-a-Brew Night, often with a gang of fellow partiers. He cracks jokes, hurls peanuts at the team mascot, applauds the exploding scoreboard, blasts an electronic horn whenever he pleases--and occasionally nudges a companion and asks, "Hey, who's winning?" The Party Rooter often wanders out of the park in the sixth or seventh inning to continue his celebrations in the car on the way home.
The Sunshine Supporter, usually a more common type than the Party Rooter, goes to the park to cheer on a winning team and bask in its glory. When the home side is on a winning streak and still in contention for a playoff spot, the stadium will be packed with this sort of fan. As long as her team is winning, the Sunshine Supporter will be roaring at every play, waving her pennant and shouting out the names of her heroes. However, as the name implies, the Sunshine Supporter is a fickle fan, and her cheers quickly turn to boos when a hero strikes out or drops a line drive. She will stay around until the end of the game to celebrate a victory, but should her team fall a few runs behind she's likely to slip out to the parking lot during the seventh inning stretch.
Diehard Fans are also strong supporters of the local team, but they go to the park to watch good baseball, not just to root for a winner. More attentive to the game than other fans, Diehards will study the stance of a power hitter, note the finesse of a quick fielder, and anticipate the strategy of a pitcher who has fallen behind in the count. While the Party Rooter is chugging a beer or dropping wisecracks, Diehards may be filling in a scorecard or commenting on a player's RBI tally over the past few months. And when a Sunshine Supporter boos an opposing player for tagging out a local hero, Diehards may be quietly applauding the expert moves of this "enemy" infielder. No matter what the score is, Diehard Fans...