If you can hear me, touch your nose...

This turns getting students' attention into a game! Quietly start saying things like "If you can hear me, touch your nose. If you can hear me, roll your eyes. If you an hear me, put your hand on your head. Etc. Do the actions yourself as you say them. Silly actions are fun, and the final action can be one that gets the students ready for the next activity.

Source: Chris Sheasby