When it comes to orchids different varieties have different needs but in general if growing the most common types do not overwater. One tip is to place two ice cubes on the top of the growing medium (orchids grow in bark not soil) and let them melt  slowly to water your orchid plant. Or take the plant to the sink and soak the soil once a week letting it drain before placing the orchid back on it's saucer. Watering once a week is an average. The amount depends on how much sunlight and how big of a pot you have.  Bright light but not direct sun is best and orchid growers recommend you use a slow release plant food like Osmocote so that you don't over fertilize your orchid. If you want more details for the different types of orchids contact your local orchid society by looking online. Keep growing, Marianne Binetti