The simple answer: Allow the plants to approach dryness, gauged by pot weight or by the pencil trick (the point of a sharpened lead pencil will darken with moisture if the plant has enough water), and apply enough water that it runs freely through the pot. Never allow any potted plant to "sit in its own water." Flowering plants may require more frequent waterings to make up for the greater burden of the flowers. Plants will require less water when not in active growth (generally winter months), and more while growing (generally spring and summer months.) Increased frequency of watering will not make up for a poor root system. If roots are not plump and alive, repotting may be called for (see later), or the plant may have been recently repotted by the vendor, in which case it will require raised humidity to compensate for the lack of supporting root uptake. Last, plants will thinner, softer foliage will generally require more water than those with harder, more succulent leaves. Plants with pseudobulbs (as dendrobiums and cattleyas) generally like to dry out more between waterings than will those without (as phalaenopsis.)