Utilise the entire space from floor to ceiling. Store little-used items on cabinet top-shelves, installing additional shelving if necessary/possible. Make full use of shelf dividers. Containers should be see-through, or clearly labelled, and preferably stackable.

Use drawer partitions for ease of access and maximum use of storage space. Sets of collapsible fabric boxes in varied sizes will create useful compartments within large drawers.
When buying a new bed with built-in drawers make sure these are large and easy to use. A better option may be to use under-bed storage boxes with wheels or castors, with a standard bed frame. Vacuum-seal storage bags are useful for storing bedding and out-of-season clothes.