Statistics often get a bad rap for being boring, but that is probably due to their overuse. Too many numbers in one place certainly can boggle the reader's brain. However, using a quick statistic as a hook can be quite effective in your persuasive essay. A statistic injects a bit of reality into your argument and might even lend credence to your position to some people. Make sure that the statistic you choose almost leaps off the page because, ultimately, if it doesn't quickly draw the reader into your argument, you've likely lost him for good.
A question can also function as a great hook if it makes the reader get into thinking mode quickly. It can't be a boring question and should, if at all possible, be related to something that most people can relate to. Be bold with your question. Be strong with your question. Uncover an angle to an everyday topic that jars the reader out of his complacency, if only for a few minutes. Don't forget that you should answer the question raised at some point in your essay or you'll leave your readers feeling like they've been cheated.
One way to turn a reader off is to vacillate between opinions and not really stand out as a proponent of anything. A classic analogy taken from the Bible declares that a person should be hot or cold but not lukewarm. This is a basic principle of the persuasive essay. Take a position and make it strong. Don't make the audience guess at what your opinion is until well into the piece. Come out quick and hard and don't let up.
Stating an unusual, off-the-wall fact in the beginning of your essay can serve to draw in the audience quickly, but take care that it has some basis in reality and quickly demonstrate it. Otherwise, you and your argument will quickly be dismissed as kooky. An unusual hook can carry you through the whole essay, but a haphazard one can derail your entire argument, which is not good. The whole point of a persuasive essay is to persuade the audience to see an issue from your point of view. A good hook is a crucial tool to achieve that goal.