First: Model the language;
(face right) Hi, my name is Dave. What's your name?
(face left) My name is blahblah.
Repeat 5- 10 times
(Chose 1 student) Hi, My name is Dave. What's your name? (encourage answer)
repeat with 5 - 10 other students.(Fall back to first step if not getting answers in English)
(Reverse roles- Elicit "Hi, my name is Achmed.What's your name?" from student: give reply
Repeat with 5 - 10 students. (add hand shaking routine if appropriate in your culture.)
Arrange students in two rows facing each other. Designate left hand row to be "hi" group; right hand row to be "reply" group. When they have greeted the student facing them clap your hands and indicate that first person in "Hi" group goes to the other end of the line. Repeat until they have all greeted everyone.