One reason your teen's room is a mess may be because the storage arrangement no longer works. Just try stacking sweaters for a 14-year-old in the same space where sweaters for a 6-year-old were stored, or putting ice hockey equipment where a baseball bat used to go, and you'll begin to understand that your teen's needs are changing.
Answer the Teen Room Questionnaire to help you form an action plan.
Once parents have a teenager, they often experience a tremendous urge to “help” their kids grow up by getting rid of stuffed animals and tossing out baseball cards. But what's the hurry? Teenagers are in transition, and by letting them keep one foot in childhood for days when they need it, you help make the passage to adulthood a gradual one. By letting them keep some things, you convey the message that it's okay to take two steps forward and then a step back. They'll get where they are going faster and easier if you let them. If space is at a premium, there are solutions. Ask your teen to choose the items that are most important to him. Offer to box up the rest and store the box on a shelf or in the basement indefinitely.
Based on this evaluation, make a list of some of the changes that you can make that will create a better room for your teen.
If you decide that redecorating is in order, resist the urge to make the decisions yourself. Talk to your teen. He may offer color or design suggestions, and you can let him make choices from pictures in a catalog or swatches you bring home from the fabric store.
Explain to your teen that while it's his room, it's your house, and though you'll try to let him have what he wants, you both may need to compromise. For example, if he wants an all-black room, you might suggest that black be the accent color, since you would find black walls very difficult to live with. If the two of you enter into it with goodwill, there should be a way to make each of you reasonably happy.
Re-Thinking the Space
Consider the function of the various parts of your teen's room. Most bedrooms should accommodate a dressing area with a mirror (near the closet and/or dresser), a quiet area (the bed and perhaps a comfortable chair), and a work area (a desk). Consider traffic flow from the main door to the various parts of the room. (The bed is generally the largest piece of furniture; don't place it so it disrupts flow.)
If siblings share a room, consider whether there's a way to create privacy within the shared space. Some families use bookcases as room dividers. You could also rig up some type of cloth divider. Or think about glass block (large bricks of glass). It's opaque but translucent, so it provides privacy but allows light to filter through to the internal side of the room. If the space is not big enough to divide (or if the siblings don't want a divided space), try to create separate storage areas. Having adequate space for each person's belongings can make shared living much more pleasant.