Posted: 06/01/2015 at 15:21
It will depend what sort of orchids you have. If they are phalenopsis (the most common ones sold in supermarkets and Ikea) they need to be in a light place, but not direct sunlight. They cannot bear standing in water, so I stand the pot in a bowl and water from the top once a week. Leave for an hour and then remove from the bowl, drain off excess water and put back in potholder. When they have finished flowering (mine sometimes go on for seven or eight months) you can cut the bare stem back either to a new bud or back to the base if has dried out. If you decide to repot do use orchid compost and mix with the soil already in the pot - it should be bulky to enable water to drain through quickly.
Some of the old roots will die back naturally, but you should get healthy new aerial roots appearing higher up. I think there was an article on repotting orchids in the GW magazine last month - have a look and see.