When she began her work-at-home career as a freelance writer, Marilyn Zelinsky gave careful thought to her assignments — but hardly any at all to where she would actually do them. She began working on the dining room table, then moved into an 8-by-10-foot den off the living room. When she found herself spilling back out into the dining room, Zelinsky got serious about designing a home office — so serious that she wrote a book about how to do it, Practical Home Office Solutions. Zelinsky knew that she had a sizable potential audience: According to a survey by the International Data Corp., there are now more than 27 million people who work at home at least part-time, a number that grows by about eight percent per year. Yet the field of home-office design is still in its infancy, and there are no finely tuned guidelines about how to turn a room into a workspace,where to put which equipment or how long or wide cabinets and work surfaces should be. Still, there are some proven principles to keep in mind when putting together a home office that really works. First, whether the office is intended for full- or part-time work, or as a place to organize records, pay the bills, and give the children Internet access, choosing the right spot is crucial to its success. "Everybody makes the assumption that all they need is a little corner of a room — but usually they end up spread all over the house," says architect Duo Dickinson. He recommends that a work space measure at least 10-by-10-feet. The nature of the work to be done and the number of people using the office can also dictate its site and setup. A solo workspace may need less seating and desktop space than one the whole family will use. If clients will be coming for meetings or work sessions, a separate entrance might be useful to keep them from traipsing through the house. Visitors need their own chairs and perhaps a table, a place to hang their coat, and access to a guest bathroom, says architect Robert A.M. Stern — "unless you want them to use a family bath and risk having them trip on your child's rubber duck." Work surfaces and storage will probably need to be designed on a budget. Built-ins may be too expensive, and computer armoires won't be a good investment because they usually don't contain enough work surface — there should be at least five feet, says Zelinsky. A modular office-furniture system, which typically includes desks, computer tables, bookshelves, and file cabinets, is the most affordable option. They can be assembled much like custom built-ins, but they can also expand as the need for workspace grows, and are available in an array of styles and prices, from lowly laminates to finely finished hardwoods. "The biggest news in home office furniture is that it doesn't have to be ugly anymore," says Mark Dutka, of InHouse Furniture and Design in San Francisco. Flexibility is another advantage of modular units. "You may want to change the room around or move the office altogether," says Dutka.