Hello Pat –
Orchids start to grow more rapidly in the Spring, so generally that is best, or just after they have finished flowering. If you start to notice new growth on the base of the branches, its a good time to re-pot, however, new growth is very delicate and can easily be damaged, so great care should be taken when re-potting. When the roots begin to produce branches, they are past their initial growth stages and are less delicate. Fertilize once a week AFTER blooms have dropped off when the orchid is in it’s rapid growth stages. After growth has slowed, fertilize once a month. Water on days you don’t fertilize to flush out any nutrient build up.
Orchids such as cattleyas and oncidiums should be allowed to dry completely between waterings while orchids such as phalaenopsis and paphiopedilums that have no water storage organs should be watered before dryness occurs. It is best to water your plant in the morning to give the moisture on the leaves time to dry during the day. If any water remains in the crown (where the leaves join in the center) use a paper towel to blot the water to avoid crown rot.
Hope this helps!