What You Should Not Do To Your Orchids!
Do not water them too often, do not give them too much water & do not let them sit in water.
This is over watering, the number 1 killer of orchids. Giving them too much water or watering them too frequently or letting them sit in water keeps the potting material soggy, literally drowning the roots which then rot and die and, soon after, your orchids will die.

Phalaenopsis are particularly susceptible to over watering.

Do not let water stagnate in between leaves, especially new leaves & new growth.
Water stagnating in between leaves promotes the growth of bacteria which will rot the leaf or leaves and / or the new growth. This will
kill your Phalaenopsis and kill the new growth of sympodial orchids.

Do not subject your orchid plants to direct sunlight.
Direct sunlight will burn the part of the leaves exposed to direct sun, making them unsightly and will also cause buds to dry and it will wilt the flowers very fast.

Do not subject them to drafts from forced air heating or air conditioning or place them near heat sources.
The air emanating from heat or cooling sources is too dry and desiccates plants and flowers fast. Buds of plants placed in or near the path of air conditioning or of forced air heating or close to heat sources will dry and fall and flowers will wilt. Both in just a few days.

Do not expose them to extreme temperatures or to too low humidity.
Most orchids will fare well in temperatures from the mid 50's at night to the mid 80's in the day.
Cymbidiums need much cooler conditions: from low 40's to mid 50's at night and from mid 60's to mid 70's in the day. At higher temperatures Cymbidiums buds dry and fall!

Your orchids will do reasonably well in 40% to 60% humidity (50% to 70% humidity is ideal). If your air is too dry (below 40%) mist lightly once or twice a day the unopened buds, the leaves and the top of the potting material. This will help keep your buds from drying.