Bring a clipboard. Bring a book to read while you're waiting. Don't give up, even when schedules are full. Sometimes you may be just what they are looking for. They should come prepared to discuss anything and everything.
Lines are part of it, but no one has died from the experience.
Be confident, positive and hopeful, and things will go well. Dress professionally, relax and expect a wait. Excellent opportunity to make contacts with different school district people and to exchange information. Review and think out possible interview questions. Be familiar with questions that could be asked.