Do you absolutely need a bridge sentence? It's normally much easier to exclude it.
Okay, let's say that your topic is whether cell phones should be allowed in school. You'll develop your thesis by yourself.... you should know how to make a good thesis, but if not, restate. The hook all depends on your personality. If you are humorous, you could play and be comical to get them to laugh and catch their attention. Just naturally make a joke that relates to the thesis, includes the topic, and supports your argument. You may invite a conflict that would relate to your audience. (Imagine that your phone goes off to notify you that you have to leave school immidiately in an emergency, but you weren't allowed to have it?) You could even just state another fact as support, a statistic or a fact is sufficient.
