We have three rain barrels and we use the water from those for hand watering the greenhouse and some of the nursery beds. Unfortunately, rain barrels aren't much use in the dry weather. Less than a week with no rain will find them empty!
In the droughts (I consider it a drought if we have no, or little, rain for a month and the days are sunny) the flower beds will not be watered unless there are young plants in them. Then they will be watered by hand held hose.
If it's hot and sunny and drought conditions then I will use a sprinkler on the beds (I'm not physically able to carry water around the garden and spot watering plants is unthinkable from both a physical and time point of view). This is always done in the evenings. The lawns are never watered.
The vegetables are a different matter. I use a sprinkler for them. The different vegetable areas need different amounts of watering, which is what happens. To try and conserve water from evaporation I water in the evenings and a lot of the vegetables are grown through porous weed suppressant membrane.
This membrane serves two purposes, reduces evaporation quite considerably and does away with the need for any weeding. Each winter the membrane is rolled back, the ground dug and fresh, home made, compost put on and dug in. Then the membrane is put back again. The side effect of using the membrane is that it also warms the soil so planting can be a bit earlier.