Being prepared is really just thinking in advance and being proactive.
I keep an ongoing shopping list posted on the fridge, so I'm ready to shop at a moment's notice. I stock up on supplies so I don't have to worry about running out of them. When I buy gift wrap or school supplies or laundry detergent, I buy a little extra. When I have a few minutes to kill, I go to the card shop and pick out a few birthday cards. While I'm there I get a few sympathy cards or thank you notes to keep on hand.
Another way to be prepared is to make a list of important phone numbers and keep it in a prominent place. I list every obscure number I can think of, for instance: the dentist, phone company, insurance agent, schools, neighbors, doctors, favorite take-out restaurants and the gas company. It saves me from looking these numbers up in an emergency. Plus it's helpful info for a babysitter.
I also write down instructions for household chores that I don’t do that frequently. This serves as a reminder from year to year for things like: how to bleed the radiator, drain the expansion tank or light the pilot light on the boiler. (Yes, I live in an old house.)
What do you do to "be prepared"?