DNS & Disaster Recovery

I need to find a way to provide failover in the event of a disaster. As it stands we have two servers for each application. One is a normal server, example: SQL1 and one is a backup DR server, example: DRSQL1. No load balancing at all just two seperate servers at different sites. Both are in DNS and up on the network. I need a way to switch over from one to the other in the event of a disaster. I’m not sure if the DR servers should be listed in DNS at all until something happens, then just adjusting the DNS records should be all it would take. What is the best way.