The hook is an introduction that catches the reader's attention. Argumentative essays can start with facts, statistics, quotes, or anecdotes that reference the topic of the essay. Make sure the introduction is interesting enough to 'hook' your readers into wanting to read more. Once you've written the first sentence, you want to connect the information to what you ultimately what to try to prove by leading into your thesis statement.
Example
According to the Centers for Disease Control and Prevention, over 2,700 teen drivers between the ages of 16 and 19 died in 2010 and over 282,000 were injured. Despite their desire to want to get behind the wheel, teen drivers simply aren't ready to take on the responsibilities of driving yet.