Migrating DNS for a production site doesn't have to be terrifying, it's about managing the period between when DNS records point to an old host and then Netlify. Before go-live day, check which hostnames and sites will be migrated, ensure no blocking Let's Encrypt certificate issues, and set low TTLs for new DNS records that point to Netlify. Get a custom SSL certificate before switching DNS records to cover the site during propagation or before any DNS changes. Test the custom certificate before updating DNS records, then update the A record and CNAME values to point to Netlify's load balancer. Once migration is complete, get a Let's Encrypt SSL certificate from Netlify, which will automatically renew every three months without interruption of service.