Install low flow showerheads.  They use 30 to 70% less water and still provide an invigorating shower.

Limit showers to 5 minutes.

Fill the bathtub only 1/2 way.

Low-flow or air assisted comodes can save up to 70% of toilet water use.  If you cannot replace your toilet, place a 1/2 gallon plastic jug of water or a toilet dam in your tank.  this can cut water use by 20%.  Do not use bricks - they fall apart and can plug your system.
Check your commode for leaks by putting a small amount of food coloring into the tank.  Wait 10 minutes and check the bowl for the presence of colored water.  If the water in the bowl is colored, a leak is present that needs to be repaired.
Repair all plumbing leaks immediately.  Small drips can waste up to 2 gallons of water per hour.
Install low-flow aerators in the bathroom and kitchen sinks, saving approximately 50% waster usage without compromising performance.

Turn the water off while brushing your teeth or shaving.

If you wash your car at home, use a cut-off nozzle or turn the water off while washing.

In the kitchen, choose a water saving dishwasher, which can reduce water use by 30%.  and, be sure the dishwasher is full before running it.

Compost food scraps instead of running the garbage disposal.

Insulate your water heater and hot water pipes so you avoid running water to get delivery of hot water.