Water your Coleus plant regularly, and when possible, use room temperature water. Enough water should be provided for the plant that you can see it begin to drain through the bottom of the pot.
To check the water levels of your plant’s soil, place a water meter 6-8 inches into the soil, where it will give you an accurate indication. If you do not own a water meter, stick one finger knuckle-deep into the soil. At this depth, you will be able to accurately account for the soil’s level of moistness.