Originally Posted by echinosum

In general, you need to hardly water them at all in the darker months, just a little bit if they are looking very thirsty. Start watering about now, and reduce watering in about October. Water them weekly in the lighter months, though they should survive a bit of neglect. In the earlier period of the lighter months, you can feed them using ordinary liquid plant food diluted with twice as much water (or half th enumber of drops) it suggests on the bottle.

Though if you have a winter-flowering cactus like "Christmas Cactus", epicactus and the like, you will need to find out a specific regime for it.

Some cactus can be, would welcome being, put outside in summer, say, June to mid-September. My mother grew one about 5 feet tall like that!

I'd avoid repotting it if you can. I've lost them like that...

The most important factor in growing cactus is giving them good light. In poor light, they can grow quickly seeking the light, but what you get is a weak, hollow cactus that then collapses and goes rotten.