The baby stage. Some likes to temporarily convert a walk-in closet or a little pocket in the parents' guest room into a crib room. Keep it until the baby outgrows it, or for when the next one comes along.
A place to crash. When kids are ready for a room of their own, it's all about the beds. This is the place for bunks, trundles and twins. Everyone loves a bunk room except the mom who has to make the bunk. Even college kids love bunks when they come home and bring friends. If you don't have the ceiling height for children bunk beds, do twin beds with a trundle.
A place to land. Bunks, twins and trundles allow for more floor space. And for kids, the floor is the place to be. Whether the kids' room has wall-to-wall carpet or wood floors with a rug, the floor should offer a soft place to land, play and sprawl.
A gender-neutral palette. If kids of both genders will visit, choose gender-neutral colors, and avoid pink and purple. A room done in tans, blues and white can bridge genders.
A personal touch. To make each child feel special, personalize his or her bed with a favorite toy or stuffed animal, and a pillow monogrammed with his or her name. In shared quarters, kids like to have their own spot, a drawer or shelf or locker for stuff that's just theirs.
A place to chill. A kid-level television, and some age appropriate books can provide kids a chance for quiet time when they're tired, but not sleepy.
A place to hide. Kids love an adult-free zone. If the architecture allows, work in a magical space like a loft, hammock, clubhouse, fort, teepee, tent, pirate ship or a curtained bed.
Minimal furniture. Unlike a guest room for adults, kids' guest rooms need little furniture. Kids usually bring duffels full of stuff, and these fill up a room very fast. For seating, toss in a couple beanbag chairs; they're youthful and indestructible.
Easy-care fabrics. Save the silk and custom bedding for another room. Go for sheets that you can bleach, rugs you can clean, and not-fancy fabrics that are easy to maintain.
High lights. To maximize floor space and minimize accidents, forgo floor and table lamps and light the room with wall sconces and ceiling fixtures,.
Room to grow. Even after they're in college, kids like coming back to the same bed from their childhood. If you've created a classic neutral backdrop that has timeless appeal, you can refresh the paint color and change accessories for an easy evolution as kids grow.