First: find YOUR style and inspiration.
Strategic stacking, book ends, lots of books (we recommend a color theme here – I use all black bound books for my shelves as an example) utilize different textures like adding baskets, plants, vases, etc.
Tips: Books and bookends next to a bigger item like a bowl or vase sitting on books. Can also use accessories as a bookend. Tray or art print in middle of shelf with a plant on one side and a varying height accessory on the other end. Make sure to pay attention to height (stagger these on shelves) and width of items on the same shelf.
You want these to vary to create interest and spacing. For example, if you have a really thin and airy accessory, pair it next to a stack of books or decorative box with a solid accent piece on top. Baskets are FANTASTIC space fillers while hiding all the things you don’t necessarily want seen on your shelves. Odd number of items on shelves is a good rule of thumb as well.