If you are in the middle of some sort of promotion, wait until it is over to change the dns. I moved a site last week. It was a large site, about 700mb. It took me several days to get all the files moved. While I was waiting for the dns to re-propagate, I sent out a special offer to my list. This was a mistake. I had links failing, frustrated customers, and lost sales.

To top it all off, my main email address was running off the same domain. I had people trying to email me for...