I just did this recently. I reduced the TTL a few days before the move and I also set up Apache on the old server to proxy all requests to the new server. Look

I just did this recently. I reduced the TTL a few days before the move and I also set up Apache on the old server to proxy all requests to the new server. Look up Reverse Proxy for Apache. I turned that on when I changed the IP addresses in the DNS records. So there was no downtime. I left this up for a week and then shut it down. Worked great. Note: This site doesn't use SSL. That would make it a little more complicated.