The soak-and-dry method
Succulents and cacti grow in places where rain is rare but heavy when it comes, then the soil dries out completely before the next storm. The soak-and-dry method just copies that: water thoroughly until it runs out the drainage hole, then don't water again until the soil is fully, completely dry, not just dry on top.
How to actually check
Don't guess by the calendar. Stick a finger an inch or two into the soil, or lift the pot: a fully dry pot is noticeably lighter than a wet one once you get a feel for it. In summer that might mean watering every one to two weeks; in winter, when growth slows way down, it can stretch to once a month or longer.
More succulents die from being loved too often than from being forgotten.
Signs you're overdoing it
Leaves that turn soft, translucent or yellow and drop at the lightest touch are the classic overwatering signs, the opposite of what most people expect from a "dying" plant. Black or mushy patches at the base mean rot has already started, and that pot needs to dry out immediately, sometimes with a full soil change.
Signs it's actually thirsty
Wrinkled, puckered or noticeably shrunken leaves are thirst, not drama. A good soak will usually plump them back up within a day. The two can look similar at a glance, which is why checking the soil, not just the leaves, is the more reliable read.
