When to Use Vertical Vs. Horizontal Storage and Organization
Generally, I'm of the mind that there are two ways to store stuff in your home: vertically or horizontally. Obviously, there are all kinds of variations and approaches, but if you think about it, you're either spreading things out or stacking them somehow—it's just a matter of what will work best in any particular space.
When to store vertically
Vertical storage is the best option when you're low on space. It's why I, a small-apartment dweller, love hanging my purses on a chain instead of trying to spread them across a shelf in my closet or using an "organizational wall" to take advantage of open wall space and turn it into storage. It's great for making use of unused space, but it's not always pretty, so vertical storage is typically used in a closet or somewhere unseen. When you're stacking everything on top of everything else, your goal is functionality, not necessarily aesthetics. It's the best approach for categories of items you have a lot of, like shoes or books.
Tools for vertical storage are actually pretty abundant, but you have to think outside of the box to find them. There are the classics, like tiered hangers or hanging shoe rack shelves, but you can use those in more unorthodox and unique ways. As mentioned, you can hang your purses on chain hangers, but those hanging shoe rack shelves are perfect for all kinds of other categories, like hair accessories, writing tools, and kitchen supplies. My favorite vertical storage purchase of all time is this four-tiered shoe tree, which holds shoes upright and spins around so you can access the ones in the back. It saves so much space in my closet because the footprint is so small and, stretching upward, it only take up about as much vertical space as a coat or two. That's much better than spreading shoes out across shelves or, worse, throwing them in the bottom of the closet, and at $40.50, it's a pretty inexpensive way to save a lot of space and keep all shoes together.
When to store horizontally
You can also store things horizontally, but I'd recommend doing this when you have space, fewer items, or something to actually display. Because I live in a small space, the things I have the most of—shoes, bags, makeup, and cleaning supplies—are always stored vertically to save space. When you have fewer of something, you're freer to utilize shelving for it, but keep in mind that if you do it right, you can even display it out in the open.
Pick up some decorative storage boxes to obscure contents, as these look nicer on shelves than having everything out in the open. Also remember the rule of three, which is an interior decorating mandate that calls on you to group items in clusters of just three along any horizontal surface.
What to keep in mind
There is a lot of overlap between the two approaches. For instance, if you stack uniform storage boxes along a shelf in the kitchen: Is that horizontal or vertical storage? If you're hanging floating shelves on an empty wall to utilize that vertical storage space, doesn't it become a collection of horizontal storage? Sometimes, your storage fits in both categories, so just use the rule of three and choose what you put on those shelves carefully. It doesn't matter much, as long as you go into your organizing with a goal in mind. If your goal is to make use of limited space, opt for vertical storage when possible. If your goal is to store things you don't have much of or make storage more aesthetically pleasing, opt for horizontal.
Ultimately, keep the Organizational Triangle rules top of mind: Everything you own should be stored with similar items and given a designated spot. Figure out how much space and capacity you have for each category of item you have, then go from there.