Cyms are not true terrestrials - they grow in the organic debris on the ground - all pots and media should be well draining, tho standard nursery pots with drainage holes in the bottom are fine, they don't need slotted orchid pots. They do like to be moist. I haven't had problems waiting to repot (tho if the pots do not have drainage holes, they probably should be repotted) - Cyms generally tolerate some older media for a bit longer than some other orchids. Repot when there is new growth starting.
Lots of light during growing period (spring/summer). Ideally, they should be grown outside for as much of the year as possible, to get them sufficient light for blooming, as well as to give them a period of cool nights in fall. People who live where Cyms cannot stay out side year round usually put them outside as soon as threat of frost has passed, and bring them back inside again at first threat of frost. Many Cyms require a period of cool nights (low 50sF or less) in early fall to initiate spikes. They can tolerate short periods near/just below freezing.
Water and fertilize well during growth period.