FAQS

Your conclusion is the final paragraph or two of your paper.  According to Strategies for Successful Writing: A Rhetoric and Reader:

A conclusion rounds out a paper and signals that the discussion has been completed. ... To be effective, a conclusion must mesh logically and stylistically with what comes earlier.  A long, complex paper often ends with a summary of the main points, but any of several other options may be used for shorter papers with easy to grasp ideas.  Most short essays have single paragraph conclusions, longer papers may require two or three paragraphs. 

Here are some conclusion Do's and Don'ts from Secrets to Writing Great Papers:

Don'ts

• It shouldn't contain any new ideas
• It shouldn't offer any new examples
• It shouldn't reach any new conclusions

"Remember that everything you have to say - all your conclusions about the topic and your facts that prove them - belong in the body of the paper.  The ending merely wraps up the theme and ties it in a bow."

Do's/ideas for the content of your conclusion

• Restate the purpose.
• Sum up - Wrap up all the points you've made into one general statement.  
• Echo the lead - A favorite of magazine writers is to end by repeating an image or phrase that was used in the lead.
• Urge readers to act - Tell what they can do to learn more about your theme, or, if it applies, simply say, "Go out and build yourself one."

Research Papers for Dummies says:

Think of your paper as a plant.  You start with a thesis - the root.  You outline a bunch of subtopics - the branches.  You provide a lot of great evidence - the leaves.  Now it's time for the plant to flower - the conclusion.   ... A good conclusion shows you've done what you've set out to do - prove your thesis.  But it also goes a little further by revealing the implications or significance of the information in the paper.

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