We've had a leaking bathtub faucet for awhile and never realized just how much water we were wasting until we placed a canister underneath which filled up overnight. Our dog had gotten used to water always being in the tub and now considers it an alternate source of water beyond her bowl. At this point we realized we had to do something about it.
First make sure to shut off your water, both your main line and your water heater line. Our main line shut-off is located in our front yard near the wall and the water heater shut off is located at the water heater.
We've had plumbers snake our sewer drains before as tree roots have infiltrated the line from our house, but typically when our kitchen and bath sinks clog up we break out the plunger and gently try the clear the line. In a two-sink kitchen make sure you've covered the opposite drain opening with a rag or something to create a seal or else you will simply blow air into the open drain and not through to the clog in the line.
One of our favorite new home blogs is This Young House and their recent rain barrel project shows step-by-step how to find the barrel, make the spout, and position it properly in your yard.
If you don't have the time or inclination to monitor a rain barrel then you could also consider a drywell which will keep water away from your home's foundation as well as prevent erosion.
