The most important item may be a well-stocked first-aid kit. Make sure you have adequate supplies, medications, and personal needs for each family member. Remember prescription medications!
You might want an AM/FM radio to listen for information from public safety agencies. Make sure you have extra batteries or a radio that runs off solar or a hand-cranked dynamo.
You might need tools or instructions to shut off the gas, water, or electric service at your home. Attach the tools to the meters if possible. Learn how these tools operate before the emergency.
Search and rescue equipment might be useful. Consider a pry bar, crowbar, or other leveraging tools, some rope, face masks, loud whistle, duct tape, and a fire extinguisher.
Assemble a binder or expandable file with copies or your important documents. Make sure you include you Family Emergency Plan with names, addresses, phone numbers, and maps for local and out-of-state contacts and meeting locations. Consider including Social Security cards, passports, birth certificates, proof-of-insurance cards, insurance policy numbers, bank account numbers, and vehicle ID numbers. You could also include a set of spare keys. Store all of these in a fire-safe location (in or near your 72-hour kits), with copies in another location outside of the home.
Get prepared for the first three hours!