Time of day to water?

It's normally recommended that you water in the evening. This allows the water to soak into the ground and not be evaporated by the hot sun. It also saves the leaves from getting burnt by the sun being magnified through the water droplets.

On the down side, it brings out the slugs and snails at night.

 

It depends what you are watering and the time of season. In my greenhouse at this time of year I only water tomatoes/cucumbers in the mornings, because if you water at night the plants sit in cold humid compost and that can cause fungal problems during these cold nights. Cucumbers are especially susceptible to rotting at the base of the stem if you leave them cold and soggy overnight. I just make sure that I water the soil not the leaves for the reason Shiney gives.

Later on in the season when everything is growing strongly and temperatures don't drop below double figures overnight then I change my method.

 

I forgot that bit, John