Transition to the conclusion without specifically announcing it. For example, avoid phrases such as, "In conclusion" or "To sum it all up". Avoid hinting to readers that the conclusion is coming, and when it does come, allow the content to speak for itself.
Re-read the introduction. The conclusion should flow with the introduction and address what the introduction promised. The conclusion should also be written in similar style and tone, as that used in the introduction. Ideally, if someone only read the introduction and conclusion, the reader should understand the overall idea of the paper.
Sell your argument or topic one last time. State why the topic or argument is important. Tell the reader why the paper is important. Entice the reader to read the body of the paper by telling the reader the significance of the paper and research's content.
Sum up the paper in the conclusion. While not summarizing the paper, highlight what was important and what the "big ideas" of the paper or research were. Do not introduce anything new in the conclusion.
Propose action by the reader or encourage further study. Address research gaps or areas needing more attention. Motivate the reader to want to research the topic further.
Write a "clincher" statement that grabs the readers attention and drives the paper's message home. While this can be difficult, it is worth the effort and adds substantial strength to the conclusion.
Write a one paragraph conclusion if possible. The conclusion should be short -- yet powerful. Evaluate the power of each sentence and revise, revise and revise. When you are impressed with the conclusion, others will be, too.
Ask peers or mentors to read the preliminary conclusion and provide feedback. Peers and mentors are a great source for constructive criticism and may provide helpful insight into something you overlooked, or may have ideas on how to effectively express yourself.