Always store clean. Clothes moths and carpet beetles feed on keratin in wool, cashmere and silk, and they're drawn to the invisible traces of sweat, skin and food on worn clothes far more than the fibre itself. Everything you pack away for a season should go away freshly laundered — this alone prevents most damage.
Fold knits, hang tailoring, box nothing damp. Heavy knitwear goes folded so the shoulders don't stretch; coats and tailoring hang on broad hangers with room to breathe. Make sure everything is bone dry before it's stored — trapped damp brings mildew and the musty smell that comes with it.
Choose breathable containers. Cotton garment bags and canvas storage boxes let clothes breathe; sealed plastic traps moisture against the fibres. If you use vacuum bags for bulk, only do it with fully dry, clean items and don't leave delicate knits crushed for years.
Deter, and check. Cedar blocks and lavender sachets discourage moths but lose their potency — sand cedar lightly and refresh lavender each season. The real defence is disturbance: moths want dark, still, undisturbed corners, so air stored clothes and shake them out a couple of times over the off-season, and inspect folds and seams for the fine webbing and tiny holes that mean you've got an early problem to deal with.