First you want to water deeply so the water reaches the entire root ball of your plant and to encourage deep roots. It is better to water deeply two to three times weekly than it is to water shallow everyday. Watering shallow everyday causes your plants to grow surface roots which dry out easier. Avoid watering in the middle of the day when it is hottest to reduce evaporation of the water. The best time to water is early in the morning when the temperature is cooler. I discourage watering at night especially during the hot humid nights of summer. Having your plants wet at night opens them to fungal disease, insects and bacterial disease.
Container gardens have different requirements. The plants in your containers are more exposed to the heat, sun and wind. They dry out faster than what your plants in your beds do. Your containers will most likely need to be watered daily during the summer, possibly twice if they have outgrown the pot and are starting to become rootbound. The best way to tell is to stick your finger down into the soil, at least to the second knuckle. If it is dry, you need to water.
Taking the time to water correctly always improves your plants chances of surviving the hot days of summer. Many of them, if trimmed back and deadheaded, will provide a new flush of growth and flowers for you again in the fall.
Just remember; "Wake up your plants wet and put them to bed dry."