Install water-saving devices (which also save energy and money in heating water, energy in pumping water and the cost of supplying water), such as low-flow shower heads and aerators on taps.
Fix leaky taps by replacing washers. There are probably DIY tutorials on how to do this online so you don't have to get a plumber in to do this. My understanding is that you measure the diameter of the tap, and get a washer that matches this diameter. Be careful to get a good quality washer--not a cheap washer that is more likely to wear and leak. You may ask a shop assistant at a hardware store if you need advice.
Avoid washing clothes, dishes and your body with warm or hot water. Warm or hot water is not needed for washing clothes or dishes, as detergents are able to perform well in cold water.
There are also detergents that are antibacterial if you are concerned about that, although rinsing in cold water may wash off most bacteria. I think that the body can tolerate small amounts of bacteria, just like other animals that eat food in nature which naturally has some bacteria. But it is wise to make all reasonable efforts to avoid bacteria.
Wash dishes by hand, reusing water where possible.
When sponges and clothes get a little bit on the grotty side, rinse them out with sufficient water and place in the sun to sterilize them via UV . You can then keep on using them and repeating this cleaning and sterilizing process until they fall apart.
Buy detergents that are non-toxic and biodegradable. When washing dishes, detergent only really needs to be used to wash oily, greasy or fatty substances (as water will wash away substances that aren't oily), so you may want to try only using it in these instances.
Washing clothes with warm or hot water uses around a factor of 10 times more electricity than washing clothes cold, and the proportions for washing dishes would be even greater, although the magnitudes are significantly less. When using hot water, a kettle will boil water more efficiently than a stove, and a microwave will be more efficient than a kettle.
Use the drip-dry option on your washing machine if you have it. Whether or not you have it, when the washing has finished rinsing, you can take the hose out, put it in a bucket on the floor and let the water drain into it, then empty the water onto your garden. This will save energy in the washing machine spinning to extract water from the clothing and in pumping the water. (Typically water is pumped up from the base of the washing machine through a hose which goes into a hole in a sink next to the washing machine, and the water drains from there.) If your hose is long enough you could take the hose straight out onto your lawn or garden and let it drain.
When you have a shower, try taking a shower during the day/morning/later afternoon/evening if you can rather than at night when it is cooler. If you do this then you can wet your body with water, then turn the tap off and lather yourself all over with soap, then rinse off again and repeat if needed. I find that the best time of day to have a shower is in the morning before getting dressed for the day. But it is also ideal to meditate as soon as you wake up.
If you are comfortable washing with cold water then good for you as you will save money. Personally, I prefer hot water. However, I am going to try taking cold showers after reading this article. I had a cold shower this morning (13/10/2014). It was certainly cold, but bearable, so I plan on continuing to take cold showers. Another water-saving tip is to use a wide bucket and stand in it to capture the water which you can then use on the garden. I have made another post on sustainable water use here.
Capture water from sinks in the kitchen and bathroom with a container (you can reuse a milk or juice bottle/carton by cutting it horizontally at the widest part and using the bottom cut-off. This is also a good way to make reusable pots for plants. If you make reusable pots this way, make sure to put holes in the bottom of the container, e.g. with by putting a needle with the sharp end upright between your toes to hold it upright then press the bottom of the container down onto it. Any plastic container works well with this).
Generate your own energy.
Install solar panels and/or an electric hot water heat pump or solar hot water system. You will be better off financially if you pay the full upfront cost as you will not have to pay lease fees however if you cannot afford the upfront cost consider a lease agreement or amortisation of the panels (with your mortgage). If you cannot afford the upfront cost then a lease agreement may be best for you at present as such schemes exist, however it may be more difficult to pay back with your mortgage as legal frameworks may not exist to do so.