There are lots of ways you can conserve water in your home and garden, and they vary considerably in difficulty. You can also make lifestyle adjustments to alter the amount of water which is indirectly dedicated to your use, such as the water used in growing crops. Conserving water typically saves you money by reducing your water bill, and it is a positive contribution to the environment and the rest of the world, since every drop you save can be used somewhere else.
One of the big water hotspots, as it were, is the bathroom. You can conserve water in the bathroom by buying special equipment like a low-flow toilet or low-flow showerhead, but you can also change the way you use water. For example, you can allow urine to sit in the toilet through several uses before flushing, or you can stick a brick or large rock in the toilet tank to reduce the amount of water needed to fill the toilet tank, meaning that less water will be used per flush. You can also adjust the height of the ballcock so that the water supply shuts off earlier, filling the toilet tank part way instead of all the way up.
In the shower, you can take combat showers, in which you turn the shower on to get wet, and then turn it off while you soap, shampoo, and shave, turning it back on again at the end to rinse off. This saves a great deal of water by only using water when it is specifically needed. At the sink, you can conserve water by not running the water while you brush your teeth. You might also want to consider mounting a sink on top of your toilet tank: when you flush the toilet and water flows into the toilet tank, it flows through the sink first, allowing you to wash your hands with it before it's dedicated to flushing the toilet.
Outside the bathroom, there are lots of ways to conserve water. In the kitchen, be sure to only run the dishwasher when there is a full load, if you have one, and soak dishes before handwashing to reduce the amount of water you need to run during the washing process. Installing a foot pump in the kitchen to control the sink can also encourage people to turn the water off when they don't need it, as for instance when someone is scrubbing at stubborn grime on a cooking pan. In the laundry room, running full loads of laundry helps to conserve water by ensuring that laundry is done less often.
If you have a garden, the best way to conserve water is to plant a low-water garden using native plants which are adapted to your environment. You can also water with recycled greywater, such as water reclaimed from sinks and the laundry. Greywater tanks which can be hooked up to home plumbing systems are available, and you can also simply bail water out of the sink after you're done with the dishes and use it to water the garden. Make sure to use biodegradable dish soap if you do this, and be aware that you should alternate greywater watering with freshwater to flush out any accumulated minerals.
Taking any one of the steps above will reduce your personal water consumption significantly, and it is a very positive step in the right direction. If you also want to cut down on your indirect consumption, you can seek out products which require less water to produce. Getting animal products out of your diet, for example, will cut down on indirect water consumption, as will avoidance of water-heavy crops like cotton, coffee, and corn.