During Escrow

This is basic to anyone who is in escrow for a house and is getting a loan (which is the majority of home buyers). Don't buy any more things on credit. You could negatively affect your credit score and disqualify yourself for the loan you're working on, and have to start over...if you can.
The reason not to charge anything is that lenders typically run your credit before closing escrow to make sure you can still make all of your payment obligations. If you make large purchases during this time(the time from the acceptance of your offer to the funding of the loan), you will change your debt to income ratio and change the loan program you're eligible for. If you have marginal credit you may disqualify yourself completely, especially in today's more stringent credit market.