Some people decide when to water by the weight of the pot. I don’t recommend this technique for beginners. Growers use many different potting mixes and some are naturally heavier than others. The same plant potted in two different potting mixes with both at the same level of dryness will have different weights. If you have learned from experience just how heavy a particular plant is when it needs water, then this may be a good technique for you and that plant. Otherwise, use the more traditional method of probing the top of the soil with your finger to determine appropriate dryness before watering.