Don't fly.
Don't be pregnant.
Be at home rather than travelling or abroad.
Expect inflation & adjust investments accordingly.
Be prepared to lose household utilities. To me this means food, water, light, sewage disposal, and heat. Two weeks downtime is the max I'd expect, but YMMV. I'm certainly ready for more.
Have alternative, renewable-energy, transportation (i.e. bicycles) in case gas is rationed.
Get triple prescriptions of medications.
Get paper documentation of all liabilities & assets. You may need to prove that you do, in fact, have a retirement account and no, you don't owe 90 years of interest on your car loan.
Know your neighbors. Now is a good time to start a neighborhood watch if you don't have one already.
Learn COBOL, because there's tons of money to be made.