Get rid of what you don’t need. Examples are old books, clothes you don’t wear, kitchen items you don’t use, toys your kids don’t play with and so on.
Buy things that have multiple uses. A head tube can also be wristband, neck gaiter, or a facemask.
Buy furniture that has built in storage space. A flat topped trunk could serve as a coffee table and also as storage.
Buy smaller. A compact microwave is what most people only need in the first place.
Buy foldable furniture like sofa beds and flip down desks. Use foldable cots for company. A card table and folding chairs can serve as extra table space when company comes.
Buy items that will store compactly such as stackable glasses or chairs that stack.
When saving things for future use, keep only the small parts. Nuts, bolts, zippers.
Think square. Square storage items fit more efficiently in a freezer or fridge.
Think vertical. The space above something can be used for storage. You can put racks in your garage to store items such as a bike or tools.
Share ownership. Perhaps you could go in with a neighbor or family member.
If you get ice at the grocer, expect to pay > $2. We save ice packs whenever we order cold food online (goldbelly and misfits). You can also fill up empty plastic juice containers or plastic soda bottles.