Answer:
There are some cautions we want to keep in mind as we fashion our final utterance. First, we don't want to finish with a sentimental flourish that shows we're trying to do too much. It's probably enough that our essay on recycling will slow the growth of the landfill in Hartford's North Meadows. We don't need to claim that recycling our soda bottles is going to save the world for our children's children. (That may be true, in fact, but it's better to claim too little than too much; otherwise, our readers are going to be left with that feeling of "Who's he/she kidding?") The conclusion should contain a definite, positive statement or call to action, but that statement needs to be based on what we have provided in the essay.
Second, the conclusion is no place to bring up new ideas. If a brilliant idea tries to sneak into our final paragraph, we must pluck it out and let it have its own paragraph earlier in the essay. If it doesn't fit the structure or argument of the essay, we will leave it out altogether and let it have its own essay later on. The last thing we want in our conclusion is an excuse for our readers' minds wandering off into some new field. Allowing a peer editor or friend to reread our essay before we hand it in is one way to check this impulse before it ruins our good intentions and hard work.
Never apologize for or otherwise undercut the argument you've made or leave your readers with the sense that "this is just little ol' me talking." Leave your readers with the sense that they've been in the company of someone who knows what he or she is doing. Also, if you promised in the introduction that you were going to cover four points and you covered only two (because you couldn't find enough information or you took too long with the first two or you got tired), don't try to cram those last two points into your final paragraph. The "rush job" will be all too apparent. Instead, revise your introduction or take the time to do justice to these other points.
Here is a brief list of things that you might accomplish in your concluding paragraph(s).* There are certainly other things that you can do, and you certainly don't want to do all these things. They're only suggestions:
include a brief summary of the paper's main points.
ask a provocative question.
use a quotation.
evoke a vivid image.
call for some sort of action.
end with a warning.
universalize (compare to other situations).
suggest results or consequences.
