1. Use the Full Height of the Space 

When you want your space to really work for you, start by looking up. If the ceilings are high enough, you can quickly increase usable floor space by building a loft bed. 

If ceilings are at least 8 feet tall, you can fit a sitting area beneath the sleeping area. If you've got 9 feet or more, then there is probably enough height for stand-up space beneath the bed. Ikea sells thin foam mattresses and wooden slats that can save valuable inches in the sleeping area. 

Even if you don't have enough height for a sleeping loft, you may have room for storage high on the walls. Adding a second row of upper cabinets in a kitchen is an old design trick for gaining storage. Apply the same thinking in your small space and you'll see storage opportunities everywhere.