This activity works well at the beginning of the year or when encouraging students to change seats.  
Greet students at the door.
Encourage students to see the instructions posted in the room.
Encourage students to get to know one another.  Seating arrangement will play a role.
Example 1:  "Sit in birthday order for all to see.  The person whose birthday is in January should sit in seat 1 or in the far left of your table."  When everyone is seated in order, the person in the last seat of the table should raise their hand. 
Example 2:  "Sit in alphabetical order of your favorite snack food."  Then, continue to follow the directions above.

"Where do I sit?" challenge