Do you know how much water you might use in a regular day? The average figure for water usage here in the US is about 90 gallons of water. This can be pretty concerning when you think about how fresh water is a dwindling resource today. A large part of the problem is old appliances and bathroom fixtures.
An old-fashioned toilet for example might use up to 7 gallons of water in a single flush. The same goes for an old non-aerated faucet which uses significantly more water when it is running.
Upgrading these items could make a huge difference in your usage. If replacing your toilet seems like a major project, it is possible that you could replace just the flushing mechanism to make it more efficient.
You should also consider the way you use water. Do you take very long showers? Do you leave the water running the whole time you are in there?
Turning off the water while soaping up, while brushing your teeth and when stepping away from a sink will go a long way towards water conservation.