For some expository and argumentative essays, it’s appropriate to end with a call to action as your last sentence. For example, if you’re writing an informative essay about the sea creatures that live in the very deepest parts of the ocean, you may close with a sentence like this: “It’s clear that today’s scientists should continue to observe and document these mysterious creatures, so we may all learn more about life at the bottom of the ocean.” A call to action like this can make your reader feel inspired and informed after reading your essay.
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.