Once the contractor has been selected the architect must prepare the contract for execution (signing). The owner and the contractor should sign the building contract before any building work commences. In some states this is mandatory for residential work.
The ideal place for the execution of the contract is at a joint meeting between the parties, preferably in the architect's office. While not a party to the contract the architect can act as a witness to the signing if required and, in the process, will be able to ensure all documents are correctly signed, dated and initialled as appropriate by both parties.