What an interior designer does: A designer envisions, plans and outfits spaces in a way that makes them both beautiful and functional. He or she balances aesthetic considerations with structural planning to reflect the clients' lifestyle, set the desired mood, complement the home's architectural features, and ensure that less glamorous details (like electrical outlets and air vents) fit into the scheme. An interior designer also cultivates relationships with trusted artisans, vendors and others who execute the design. When to hire one: You may have a clear vision for your home, but an interior designer can help you bring it to life while making sure it satisfies nitty-gritty considerations such as space planning. A trained eye and a creative mind-set allow for devising solutions that you might never have imagined, and attention to the tiniest details will transform your space into a haven that looks polished and pulled together.