Use summarized statements. During your conclusion, you need to summarize what you've said during your speech. A quick overview of your main points is all it really takes.
Don't include any new information. A conclusion should simply review what you've said and give your last opinions.
Be brief. Don't make the conclusion too long. It's suppose to wrap everything up and signal the end of your speech. Your audience won't be pleased if your conclusion is long.
Take your time and don't rush through the conclusion. This applies to both the writing and the delivery of the conclusion. Rushing through it will take away from the affect it's supposed to leave.
Develop different conclusions and pick the one that you think is best. Come up with a wide range of conclusions and choose that leaves the audience thinking. Have a few people give you their opinions of the conclusions that you've produced.
Your conclusion should leave an impact on your audience. There are many ways to do this and it is your job to think of one that will leave your audience thinking about your speech.
Write your conclusion out entirely. By doing this, you can know what you're going to say so that you don't have to make it up on the spot.
Memorize the conclusion and practice it. Your conclusion should come out smoothly and sound convincing.