Here’s How:

1. Start looking in your child’s favorite books, magazines, decorating books, and even get ideas online. You’ll get great inspiration for a theme.
2. Be sure to involve an older child by getting his or her ideas and choose favorite colors, favorite sports or artistic interests, or story or movie characters, like Harry Potter or Spiderman.
3. Shop for fabric, wallpaper or border paper that will reinforce your chosen theme. Select a main print that will set the tone for the whole room.
4. Choose a background color to use on the painted walls, floors, and ceiling. Use your main fabric print to guide you.
5. Select coordinating fabrics, accessories, and prints that mix well with the main fabric. Use the colors in the print for inspiration.
6. Choose a focal point for the room. While many choose the bed as the main point of interest, you could focus on a display shelf, a painted wall mural, or decorated play area. The focal point should really reinforce your chosen theme.
7. Use some imagination when selecting and planning on decorative elements. If your child loves tennis, string a net behind the bed for a headboard. You could arrange tennis rackets (collected from tag sales or flea markets) around the netting. Place tennis balls onto the tips of clothes hooks. You might use a section of picket fencing for a headboard in a cottage style room.
8. Choose bedding that will enhance both the color scheme and theme you’ve selected. Pretty flowers work for almost any girl’s room scheme and blue chambray fits with most boy rooms.
9. Be sure to save a place to display your child’s artwork, collections, and projects. You can set them on well-placed shelves or make an artistic display on the wall.
10. Don’t forget to save plenty of room to store clothes, books, toys, games projects, and hobby supplies. A child of any age needs a desk for a computer and school work. If the storage items will be out in view, be sure they’re decorated to fit the theme, too.
11. Create a window treatment that enhances the theme and adds to the decor. Decorative hardware on doors, drawers, and cabinets can continue the theme.
12. A good rule to follow for a themed, coordinated room is to repeat each color, fabric, and print, if possible, in at least three places around the room. If you do, everything will really tie together.

Tips:

1. Safety should be of primary consideration when selecting items for a child’s room. Keep electrical cords out of the way, use non-skid pads under decorative area rugs, and don’t stack storage units too high.
2. Using coordinating colors in all elements of the room will bring even unlike things together to support the theme.
3. Use a common background color when you use several coordinating prints in one room. Choose patterns and prints in different scale, such as a large sailboat print with smaller coordinating plaids and stripes.
4. You can create inexpensive framed art by using your child’s own artwork or cutting pictures out of books or magazines.

source: about