How do you start formulating a disaster recovery strategy?

I prefer to call this a 'Business Continuity Plan' , and that will help you to think better about your needs. ( I run across a LOT of small businesses that think Disaster Recovery is only putting in a backup tape and doing a restore )

First thing you need to do is to survey your business. You will need to decide what people, processes, and resources are most critical to maintaining your operations, and focus on that as your primary concern. Do you have a proper contact list for those people identified as critical to your operations ? And is that list, if it exists, in distributed or protected locations. How about a list of critical customer facing phone numbers and internet sites ? Contacts for the utilities ( telephone, data circuits, electrical & gas, HVAC, etc ) ? Do you have access to financial support ? (ie, emergency credit cards or bank account for emergency purchase of replacement equipment and services, you do not want funding issues to cause days of delays ). How about a vendor list where you could procure replacement services and equipment, or even procure loaners ?
There are some good resources for Disaster Recover and Business Continuity. I belong to the Southeastern Continuity Planners Association ( I was on the executive board for 7 years) , check out their web site for links to other resources : http://www.scpa-us.org .
This barely scratches the surface of what you should start with, and you'll notice there is no mention of any technical details, as those can be firmed up AFTER you set your priorities. At least this should give you a bit of direction for your discovery.