Size up Your Space
Beginning with the left wall, measure everything to a T.
Sketch a to-scale layout on graph paper, with each wall's width and height as well as details such as base moldings, chases, and receptacles.
Make note of sloped ceilings, knee walls, and other old-house oddities. If facing walls aren't the same length, at least one angle isn't square.
Divide and Allocate
Start with storage for your shoes. While options include slide-out racks and tilted shelves, your best bet is open shelves without dividers. To squeeze in an extra pair, alternate toes-facing-out and toes-facing-in.
Sketch in rods for shorter items, making them as wide as your wardrobe warrants, and a higher rod for longer items.
Draw shelves 4 inches above the rods plus a high shelf for less-used items, and mark their depths.
Look for Nooks
Allocate space for a folding stepladder, against the wall under the highest rod, say.
See if there's space for a robe hook on a return or side wall.