Accumulate the vegetable and fruit trimmings and other waste before you use the garbage disposal. Dispose of all the waste at once, flushing with cold water. Use a little water and a lid on the pot when cooking most food. Water conservation doesn't stop in the kitchen. If you have a fish tank, save the dirty water to use on your house plants.
Fish emulsion is a good and inexpensive fertilizer high in nitrogen and phosphorous.
You will be getting two benefits in one - fertilizer and water savings. A drip or a leak anywhere inside or outside the house can waste hundreds of gallons of water per day. Check all water line connections and faucets for leaks. If they are leaking or dripping, tighten the connections or replace worn washers. The care and cleaning of the family car is another way to save water.