Without being facetious, google for disaster recovery plan! Disaster Recovery is very company specific (unless you are under a regulatory body, such as banks are in the UK). There nearly always a balance of risk against cost. I skimmed this and it looked a likely place to start:
http://www.disaster-recovery-guide.com/[
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Personally, it sounds like the most basic thing you need are at least two load balanced servers, so if one goes down you can take it away and repair/replace, leaving the first server to continue. But that isn't really disaster recovery, more fail-safing. The other thing is that you might find the application you have is unsuitable (server-based session don't work on most load-balanced environments for example).
If you are interested in more robust disaster recovery the you then have to consider whether an off-site mirror of your site is appropiate. You might find companies where you are that host this for you.
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