In case we won one of the printers in first chose lottery. What is the procedure for canceling the order and receive back the 600 points
You haven’t entered it yet, have you? If you haven’t entered it, and you don’t want one of the FIRST Choice printers, you simply don’t enter. Spend your FIRST Choice credits on something else that you can use.
There isn’t one. If you put in for a printer, and get one, it’s a final decision. The lottery is not done yet, so if you are unsure, don’t enter the lottery.
For other people who have this question, the official answer is you can’t cancel the order. http://forums.usfirst.org/showthread.php?21152-3d-printer-lottery