To save water get a low flow shower head and when using the sink use the lowest flow rate of water. If possible, spend less time in the shower.
To use less water in the laundry, consider using the bath towels for a few days instead of using clean one daily.
For energy savings, if possible do not use a ventilation fan, instead, open the window whilst having a shower, so the steam and water vapor are removed by natural ventilation. Also, if possible keep the window open for a period after you have finished in the bathroom, giving more time for the water vapor to be ventilated out of the room. The window doesn't have to be wide open, but sufficient to allow natural ventilation of the room to occur.
If you don't need to, don't use a heater while in the bathroom, and use low energy lights. Using low energy lights does not mean having reduced lighting. Some light bulbs produce a lot of light for small amounts of electricity.