Thanks Baja, great topic!
The first thing I've learned about watering cactus and succulents is that it is crucial to have a pot and soil combination that will drain very quickly. It's also important to never leave a plant sitting in water.
Given the right pot and soil, my watering also depends on the type of plant and season of the year.
It's very hot, dry and bright here through the summer. My plants are outdoors in a screened porch, but get a little direct sun in the mornings and late afternoons. I water at least weekly, soaking the soil and usually making two or more passes, as Baja recommends. I watch the plants for signs of dehydration--wrinkly, droopy leaves or grayish coloration, and up the watering as necessary. In fast draining soil, this has not led to any rot issues.
Winters here are cool, less bright, and mostly dry. The cactus and succulents go into an unheated shed, with a south window and a grow light. Everything gets a thorough watering once a month--soak it, and make sure it drains. The succulents and small starter plants may get a second watering about mid-month, if needed. With the cool temps and shorter days most plants are semi-dormant and don't need much water. I may not water at all from December first to mid January.
As the seasons change, I gradually up the watering as the weather warms in the Spring, and cut back in the Fall. There are of course some tropical succulents that need to be treated differently, that's another story.
Cactus and succulents are very well adapted to their native conditions. Hot temps, bright light, dry air, and intermittent water are what they require, not what they "tolerate".
