First of all, the kitchen of an old house (one built before World War II, for instance) was generally designed without adequate knowledge of housekeepers' work methods. In recent years, domestic science experts have uncovered a great deal of information on exactly where each kitchen appliance should be to help a housewife do her jobs with minimum steps and maximum efficiency.

Secondly, old-time kitchens were put together with few if any of today's modern labor-saving conveniences. For instance, few were built to accommodate dishwashers, oversize refrigerators, separate range and oven units, etc. Old kitchens had none of the many modem materials such as plastic countertops and tile flooring which simplify home maintenance.

On the other hand, old kitchens usually have a wonderful ingredient. They have space - more of it, generally, than can be found in any but the highest-priced homes of today. And with space in a kitchen, you can achieve marvels.

A kitchen needs only three doors - one to the hall, one to the dining room, and one to the outdoors. Extra doors are undesirable. They create traffic problems, and each door takes up about three feet of floor space. That space usually can be put to better use as a closet area. It could also be used to house a clothes washer or dryer.

An unnecessary door usually breaks up the wall space and makes it hard to get an efficient, unbroken countertop arrangement. Instead of having a long, continuous counter - which aids greatly in preparing meals - you may be forced to buy two separate countertops. Two separate units usually cost much more than a single unit occupying the same area.

Don't be awed by the job of closing off a door opening. It's easy. Just take off the door along with the jamb - the wooden pieces along the sides of the opening - and the trim around the sides. What remains is the rough framing of the wall

Now all you need do is to lay a 2x4 flat on the floor along the width of the opening. Then nail vertical 2x4 studs to it - one against each side of the door frame, and the third in the center of the opening. You will now have a surface to which you can nail wallboard, gypsum lath to serve as a plaster base, or whatever wall-surface material you intend to use.

It may help to close off an existing window as well. Generally speaking, it's best to get as much natural daylight into the kitchen as possible. But sometimes small kitchen windows detract rather than add to the overall value of the room. They take up space which could be better used for wall cabinets.

If you close off a window, use the same basic procedure as is used in closing off a door. You will have to provide a framework in the opening - not only for the interior wall material but for the outside one as well. Since exterior wall materials (except brick) have a tendency to fade, you'll probably find that you can't match colors with the older stuff. This difference should not cause great concern: The difference will vanish next time you paint.

With some small alterations such as these, you can have a brand new kitchen in your home.