That all depends on how much data you can afford to loose and what sort of systems you have in place.
For a small business the most common solution would be to use database mirroring to replicate the database to a DR site.
Larger companies will use storage based replication or something similar to replicate the data.
The first question in any DR discussion is how much data can you afford to loose and how much money do you have to spend on the solution. The smaller the first number, the larger the second number will need to be.