Ahhh saving water... Here in Aus we know all about it!
We have two 20,000L tanks, plus a few smaller ones (all filled with rainwater from the roof of our house, carport and two garden sheds), and a bore. One of our tanks is specifically for grey water. We're also on town water, but we have quite an extensive garden and because of watering restrictions we use our own tanks to water the garden, vegies and chooks.
One of the best things to do is to hook up all your grey water to a tank. If the plumbing is too ridiculous to fix the whole thing up, then just bring a bucket or two along with you every time you have a shower - once you're done, let it cool, and then stick it straight on the garden! The same can be done for your laundry - stick your washing machine hose into a bucket rather than the drain, and use the run off. It would probably help to use environmentally friendly soap, especially if it's going on areas of the garden that either you or animals will be eating. If it's general water usage all-round that's also a problem, put half a brick in the cistern of your toilet - that way it's always a 'half' flush. Also keep showers to under 3 minutes, and install a water-saving shower head. Using a dishwasher is actually more water-efficient than doing dishes in the sink.
Ummm that's all I can think of for now, but I'm sure more will come to me! Saving water is something that comes naturally to a lot of us Aussies...