Water when the top 25% of soil is dry when the plant is actively growing. Water thoroughly and discard any excess water. If the plant is in a dormant state, water sparingly only when the soil is all the way dry to prevent the tuber from drying out. Soggy soil will cause tuber rot and the eventual death of your plant.
Caladiums are not cold hardy plants and do not do well in temperatures below 65°F. Prolonged exposure to cold temperatures will cause the plant to wilt. Try to keep them in an environment around 65-80°F in a warm humid spot away from drafty areas or open vents.