Everyone who grows plants of one kind or another has their own ideas about how to take care of them. Cactus growers are no different! However, the best advice I can give you comes from my own experience, hook or crook, or more often than not, just plain luck! What I did over a period of years, was to learn by trial and error, reading, asking, and watching. As a result of all this, here's what I do.
WATER: Where I live in the Central Texas Hill Country, I water my plants April through September, once a week on Saturday morning. I am prudent in doing this by watching the weather and not watering if it's going rain; don't over water, and don't water at all if there appears to be something wrong with the plant. Cacti are plants that have evolved to their natural habitat and trust in nature to take care of their watering. They can go long periods of time without a drink of water. Remember, cacti do not like "soggy chairs" to sit in, so it's always better not to water when in doubt!
AIR: If your plants are in outdoors pots or planted in the ground, there is nothing more to say. But if they are planted in pots indoors, then they will need circulating fresh air. If at all possible, a window or two should be partly open for a while during the day. Like the desert from where these plants come, they basically like warm days and cool nights. Don't go to any extremes, i.e. never set your plants close to a fire; just use common sense!