Cigars need three things from their environment: stable humidity, stable temperature, and protection from light. The numbers I would give a new owner are sixty-five percent relative humidity at sixty-five degrees Fahrenheit, held within a few percentage points and a few degrees year round. The traditional seventy-seventy rule (seventy percent at seventy degrees) is serviceable but a touch high for modern tastes; the burn slows and the ash flakes at higher RH.
The vessel matters less than the conditions inside it. A well-seasoned Spanish cedar humidor is the conventional answer, but a tupperdor (an airtight food-grade plastic container with Boveda packs) is just as effective for working storage and far more forgiving in dry climates. The non-negotiable is a calibrated hygrometer; analog gauges drift, and a digital hygrometer that has not been salt-tested is lying to you.
Two common mistakes: humidors placed on top of refrigerators (the heat cycles the box) or against exterior walls in cold climates (winter cycles the wood). Pick a corner of the room that is consistently cool and out of direct sun.
The full case on humidity, temperature, and beetle thresholds is in How to Rest a Cigar.