Link the conclusion to a point made in the introduction. This technique -- favored by journalists everywhere -- is especially valuable if you have introduced a person or a problem at the beginning of the paper, perhaps in the form of an anecdote. Such "springboard" approaches allow writers to dive into and develop their paper. Fishing out that person and giving him prominence in the conclusion can give the reader the idea that you haven't forgotten this anecdotal resource and that (more importantly) the paper has come full circle.
Invoke a quotation that summarizes the main points of the paper but expresses them in another way. Such quotations can come from novelists, historians and political leaders. Be certain that the quotation is not only pithy and clever but also captures the point of the paper.
Rally readers with a call to action, or an act that you wish readers to undertake. Since you probably haven't written the final, definitive word on the topic, a call to action can be particularly effective if it points forward and provides at least a stop-gap remedy to the issue at hand. For example, an essay on funding shortages at a shelter for domestic abuse victims might end with a call to action for readers to volunteer their time or make a monetary donation to the shelter.
Develop a logical forecast, recommendation or warning if a call to action strikes you as too heavy-handed. This technique, too, offers the opportunity for the paper to "point forward" and to leave the reader with something to think about -- an attribute of a well-written conclusion. Using the example from above, a conclusion that employs facts and figures to project that the shelter will close in six months if funding sources dry up could serve as an effective forecast or warning.
Write a truthful and eloquent anecdote that captures the points and spirit of the paper. This technique should be attempted only by skilled or confident writers -- not by the faint of heart, for the tone must be spot-on. Credibility and believability are earned rights, and those that a writer does not want to forsake at the very end of a paper with an off-topic anecdote.