1. Double up on hand sanitation. Fill a spray bottle with liquid castile soap, water, and a plenty of tea tree or other anti-bacterial essential oil. To wash you hands, spray with a generous amount of your soap/tea tree mixture then rinse with water from a filled sink or a container of (clean) water set next to the sink. Use hand sanitizer.
2. Take a "sponge bath" using a washcloth and soap. Or use no-rinse baby wipes.
3. Stock up on disposable plates, cups, and eating utensils. Cleaning up after meals will be a challenge and will use a lot of water. Save the water you have for cooking utensils and use disposables for everything else.
4. Clean with cloths and rags -- not sponges. Without proper cleaning, sponges will become unsanitary quickly.
5. Dispose of toilet paper into a wastebasket and not into the toilet. This will prevent your toilet from backing up because it is crammed with paper. When it comes time to flush, fill the tank with water and use the handle on the toilet to flush. This uses less water than dumping water into the bowl.
6. When there's advance notice of a water shutoff, you can fill the bathtub and spare jugs and buckets with water. But when it's sudden, you won't have time. That said, take notes, and use this as an opportunity to take stock of what you'll need to have on hand next time there's a water outage.
Lots of disasters including flooding and tornadoes can shut down water supplies for short periods of time, so it's not just broken water mains that you need to think about. If you don't want to be one of those people fighting it out for the last case of bottled water at the grocery store, plan ahead. FEMA recommends at least one gallon of water per person, per day.