Watering wisely is all about understanding your garden and what it needs.
First, put away the hosepipe! These are great at delivering large quantities of water BUT when resources are limited they shouldn't be used, as it's too much.
Instead, do the ' can can', and use a watering can. This encourages targeted watering, ensuring you are only watering what's necessary at the moment. Well-established plants within borders will need little if any, water. New planting and pots and baskets will need water so direct your energy in their direction.
And the bonus of using a can... you get your steps in!!
Think about feeding. Plants need feeding, particularly when they are being watered as this can wash the nutrients out of the pots quickly. If flowering plants use tomato food, and if foliage then use miracle gro.
It's all about timing! Don't water in the morning or during the day. Do it in the cool of the evening. This reduces the amount of moisture lost to evaporation and gives plants plenty of time to drink.
And as for the lawn, leave it! unless it is newly sown or freshly laid turf, you shouldn't be watering the lawn. They will recover quickly when the rain comes, which will come soon enough for us.