Regardless of the paper topic or your beliefs, stand by your supporting arguments to finish with a strong conclusion. Never apologize or second guess your main points at the end. Refrain from using phrases such as, "I may not be an expert," or "At least that is what I believe." This will make your paper and your arguments appear weak and indecisive, discrediting your work.
A conclusion should be used to pull together the paper. It should not be a platform on which to introduce new ideas. Introducing a new point in the conclusion does not allow you enough space to fully explain. If you have additional points to make, throw them in with the body of the paper where they belong. This will also free up space for your conclusion to make an impact.
You want your paper and the points and facts contained within it to be remembered. There are various strategies that can be employed to make this possible. Try ending with a quote. Quotes can be both inspirational and quite effective. Another option would be summing it up with a brief story. An anecdote can provide real life perspective and illustrate for the reader the impact the paper could have on him.
Get to the point. After choosing a strong strategy on which to end, do not get caught up in explanations. Simply say what needs to be said. Additionally, do not hover between two different types of conclusions. This only draws out the conclusion while confusing the reader. The reader has stayed with you up until this point already. Reward her with a strong conclusion that pulls the entire paper together.