Retaining student attention in class.. a big challenge. Simple Tips:
* Maintain eye contact - ensure that students know you are watching them
* Maintain positive body language - stand or sit straight, not leaning
* Use positive language - helps students maintain positive attitude in class
* Ensure everyone is attentive - check with questions & quizzes (for e.g., www.inquizitor.com http://ping.fm/W8scZ)
* Be tough but handle easy - the objective is not to antagonise but to assist students.