Aloe vera
Aloe stores water in its leaves and is happiest when the soil dries out completely between deep waterings. Mushy leaves are almost always a sign of too much water.
Short answer: for an aloe, with the starting settings below (a 6 inch pot with a drainage hole), check the soil about every 6 to 9 days in spring and summer and every 9 to 14 days in winter, and water when the soil is dry all the way through. Give it a full drink until water runs out the bottom.
Your answer
Water when the soil reaches this point
How it shifts through the year
Water slowly until water runs out the drainage holes, then empty the saucer within an hour. The right amount depends on pot size, so go by drainage and how dry the soil is, not a fixed measure. Soak thoroughly, then let the soil dry out completely.
Every couple of weeks in a bright room is a common starting point, but check that the soil is fully dry first. In winter it may need water only once a month.
Overwatering is the usual cause. Let the soil dry fully, and cut away rotted tissue if the base is soft.
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Related guides
Estimates use rules of thumb. Always confirm with your finger: push it about an inch into the soil before you water.