Plants require regular watering.
Rule of thumb: Your in-ground plants need 1" of water per week. While it's best if mother nature does the job (think a good soaking rain lasting for several hours). Pots in direct sun tend to need water every day, maybe even if it rains, because they dry out quickly.
Watering needs are greatly affected by the amount of rain, the amount of sun, the type of soil, the humidity, the type of plant, and the location of the plant or pot. An experienced gardener learns to spot the differences but it can be a big challenge for the average person.
Another rule of thumb: Water in the morning. Midday heat can lead to a lot of evaporation and even boil your plants. Evening watering often leads to plant diseases.
Deep watering allows sturdy deep roots and healthy plants that can deter pests and diseases. Healthy plants produce more flowers, fruits, and vegetables.
Although it seems counter-intuitive, more plants are killed by too much water than too little. Roots need air and water can plug up the air pockets in your soil. I recommend that you include a couple inches of stones in the bottom of your pots and always have a drain hole in your pots to allow for water to escape.
Final rule of thumb: Annuals need soil that is moist at 6", vegetables 6" to 12", and most perennials will thrive with moisture as low as 12". Pots should be moist within a couple of inches from the top of the soil. Don't ever let them dry out completely.
If you are planning to be away from your garden or simply need help with your watering, please contact a professional service like Sit. Stay. Grow. to help you keep you plants healthy and happy.