The best way is to learn what your plant "feels" like when it is damp, and what it "feels" like when it is dry. The way to learn is once you have watered your plant, pick it up. It will feel heavy, the weight of the water adds to the weight of your plant. A couple of days later, pick it up again. It will feel lighter. After doing this for a week, you will know what a light (and dry) plant feels like, and what a heavy (watered) plant feels like.
Although an African violet does not like to go completely dry, they will tolerate it, but will not grow well. African violets will also not tolerate being soaked in water. They do not like wet feet. That will introduce root rot, which will kill your plant. The way to not over-water your plant is to make sure that the saucer your plant sits in to collect the excess water, does not have any water left in it 30 minutes after you have watered your plant. Each time you water your plant give it a quarter turn to keep it looking straight.