Before the activity starts: 

• This is the main prototyping day, so have the room set up for some productive building time. It can be useful to have all the materials and tools out in one central area "buffet-style." 
• Keep materials simple and easy to work with (so, cardboard, not wood).

Throughout the activity: 

• Check in with teams as they work. Make sure the team members are on the same page with their project. 
• Make sure the students don't get hung up on building a precise site model and therefore don't have enough time left to work on their actual design intervention. Site models are meant to be quick and representative, not highly accurate or elaborately detailed.

At the end: 

• Students should have some expression of their design in a site model, and get some feedback on that work. They should go into the final day with an idea for one improvement that they will make before the final share-out..