Make Statistics Relatable
Statistics are a great way to emphasize your points and bring credibility to your message. But raw statistics don't necessarily have an emotional impact on the members of your audience, so it's often important that you add "what this means..." to your statistic.
"According to the Humane Society, about two-and-a-half million healthy, adoptable dogs and cats are put down in U.S. shelters each year" is a startling statistic, but it's hard for many people to get their heads around how many two-and-a-half million actually is. But if you add "that's about one cat or dog that's put down... every 13 seconds" to your speech, that brings it within the comprehension of pretty much everyone.
There are a couple of other cautions in using statistics. First, make sure they're accurate. Just because you read it on the Internet, doesn't mean it's true. Nothing can ruin the credibility of your presentation more than inaccurate or misleading statistics.
And because people may be suspicious of your statistics, be prepared to cite your source. It's your choice whether or not to verbally give the source of your statistics in your speech (it can slow your speech's pace if you overdo it), but you should certainly be prepared if someone ever questions it.