Aim for an audience outside your sub-field. Department members in all specialties may attend. If you talk about, for example, U.S. Civil War history, you'll need to ensure that specialists in ancient China and medieval Europe can understand the significance of your claims.
Emphasize the connection of your topic to the field as a whole. Point out how your methods or discoveries might apply across the entire range of your discipline; or how you are doing groundwork for a larger project of broader significance.
Keep a few minutes under your time limit. Practice your talk a few times to make sure that it won't run over. Bracket a few sections that you can present if you are on schedule and omit, if you fall behind.
Ask detailed questions about the course for which you are preparing a sample class. Read up on the course and how it fits into the curriculum on the department website. Email the committee chair, if you have any specific questions about what you should prepare.
Prepare several self-contained five-to-10 minute mini-modules, so that you can add or drop an extra module if needed. By having separate mini-modules, you can speed up an activity that doesn't work, or add more time to an activity that engages the group of students.
Explain the purpose of each activity and how it fits into overall course objectives briefly, before you start.
Engage the students. The main concern of the hiring committee -- concerning your teaching skills -- is how well you interact with their student body. You demonstrate expertise in scholarship in your writing sample, research talk and interviews; a teaching demonstration shows whether you can relate your knowledge to the needs of the undergraduates.
Pay attention to time as you talk. The time limit you are given is a maximum, not a minimum, and you don't want to rush the question session.
Focus on communicating. Maintain eye-contact with every member of your audience and project your voice. Slow down and try to read clearly. It's better to omit a section than to appear rushed.
Be polite and respectful to everyone during the question session. If an undergraduate shows up and asks a rude or bizarre question, show that you can handle it courteously and intelligently. In your career as a professor, your job is to deal with all types of student questions in a calm and professional manner -- and you need to demonstrate that ability in your job talk.
Think carefully about questions which seem to be more about the questioner's own research than your talk. People want to know if you would be the sort of colleague who can talk with them about their projects, rather than just giving monologues about your own project. If you talked about Marlowe, and someone asks a question about Moliere, for example, show how your work on Marlowe can relate to their work on Moliere.
Don't fake knowledge. If you can't think of an answer or haven't read a specific piece of research, it's perfectly acceptable to say "I'll need to get back to you on that." Ask for the questioner's email, and send an answer in a day or two.