Pair up students and tell them to decide who will start talking. On cue, announce the topic and student A in each pair starts talking about it. Then, clap your hands once to signal that student A should stop talking and student B should immediately pick up from there and start developing his/her ideas on the same topic. This step is repeated 3-4 times, each time giving each student about 30-45 seconds to talk. Simple and very broad topics should be chosen, such as: chocolate, family, work, etc. However, more challenging topics can be chosen, such as: love, pencil, rivers, doctors, freedom, etc.
Tip: Vary the length of time each student speaks.
Picture Credits: Flickr (ah_blake)