There are some things to avoid when you design your space to fit your needs.Pixel-Shot/Shutterstock Interior designers told Business Insider the best and worst ways to use extra space in your home. Bookshelves can provide extra storage, and you should take advantage of windowsills and ceilings. A built-in unit or cabinet can lower the resale value of your space since it's less versatile. Whether you rent an apartment or own a home, it's essential to consider how your design choices allow you to make the most efficient use of your space.