Ready.gov is a great source of information when planning for an emergency. The site below has various PDFs and printables that will help guide you through creating an emergency plan.

https://www.ready.gov/make-a-plan

Marines.mil is also an excellent source for planning. Similar to Ready.gov the layout is a bit more compact and includes PDFs and printables as well.

https://www.ready.marines.mil/Make-a-Plan/Making-a-Family-Emergency-Plan/

The Red Cross also has a plan template however it is more of a form than a guide. If you aren't already familiar with plans this may be a rough start.

https://www.redcross.org/get-help/how-to-prepare-for-emergencies/make-a-plan.html