The most basic disaster plan every household should have is the plan for their family. Start HERE to learn about how to start your plan.
Your basic disaster plan should include measures for both sheltering in-place and evacuating.
After you've got your plan set, the next step is to build a kit with supplies you'll need in case of disaster. There are many online resources available for this, some outlining a very simple kit, others laying back what would seem like a mountain of supplies. How involved your kit needs to be is an individual decision; a good place to start is HERE.