You can think of an essay hook as you would a fishing hook: it's something that grabs a reader and reels him in. The hook for your essay could be any interesting sentence that captures attention and keeps the reader reading.
Here are a few examples of paragraphs that begin with a hook and end with a thesis sentence.
Quote: "A man's errors are his portals of discovery."
For the thesis: Students grow more confident and self-sufficient when parents allow them to make mistakes and experience failure.
Fact: Many studies show that the biological sleep pattern for teens shifts a few hours, which means teens naturally stay up later and feel alert later in the morning.
For the thesis: If every school day started at ten o'clock, many students would find it easier to stay focused.
Statistic: According to the Bureau of Justice Statistics, teens and young adults experience the highest rates of violent crime.
For the thesis: Parents are justified in implementing a strict curfew, regardless of a student's academic performance.
The good news about finding a hook? You can find a quote, fact, or other type of hook after you determine your thesis, with a simple Internet search.