One problem many speakers have is that they don't know how to conclude a talk. This is especially true when they allow time for questions at the end. At the end of the last question, they ask "Are there any more questions?" If not, they usually say, "OK, thanks for coming", and the presentation falls flat. The most memorable parts of your speech should be the opening and the closing. Always make sure you close with power. If you plan for questions at the end, tell the audience "Before I close, what questions do you have?" After the last question, go to your prepared close with power.
Here are a few suggestions for powerful closings:
Summarize Your Main Points. This brings your presentation back to their minds and the repetition reinforces the points. This by itself may not be powerful. You can add one of the other suggestions to create more power.
Leave Them With a Vivid Illustration. A strong (and short) story about how someone has used this information will drive the point home. Ask a Rhetorical Question. You are not asking them to respond out loud but to respond internally. This is a good way to get them to think about how they can use the information you have given them.
Issue a Challenge or Appeal. You can end with a call to action or what ever you want them to do with the information. This can be in the form of challenging them to reach a goal.
End With a Powerful Quotation. Quotes are one of the most powerful ways to drive home a point because you can refer to a famous person, which adds credibility to the point of your speech. | 
