First impressions begin with a step inside the door

The entrance hall is the introduction to a home. It gives visitors their first impression, and it should feel welcoming to them as well as to the family members who go and come each day.

Most decorators agree that the entry should be decorated and furnished in a way that gives a good impression as well as a clue to the personality of the house beyond. It should set a tone.

Mario Buatta, a New York designer, believes the foyer should be attractive and friendly, but not too friendly. ''After all,'' he maintains, ''an entrance hall is a receiving space, and it receives strangers as well as invited guests and family members. I try, therefore, to keep an entry somewhat simple and impersonal - sometimes, in very modern apartments, even a little austere.''

The entrance he designed a the 18th-century Connecticut farmhouse is not austere at all. It reflects the refined country look of the house itself and features sunny yellow walls covered with an old-fashioned stencil design on wallpaper. The floor is covered with informal sisal matting, which is a good neutral background and practical as well. Furnishings include a Sheraton bench and table, and a Federal gilt mirror and tole umbrella stand. Baskets full of dried arrangements are tucked under the table. The staircase and all the woodwork are painted white.

Some city clients, pushed for space, prefer to furnish spacious entrance halls as sitting rooms, using them as extensions of major living areas. Others convert them into art galleries and use the walls to show off art or photography collections. His latest trick to open out and brighten dark city entries is to have the floors painted in marbleized effects and given shiny coats of durable varnish.

Another point of view is illustrated in the entrance of a Nantucket house, where the family has arranged, in merry but organized profusion, many collectibles that they love. They are so well displayed and so full of interest that visitors often want an inspection tour on the way in. This is using entrance space to the hilt of its exhibition potential. Many people prefer this look to that of uncluttered simplicity.

All approaches work, but experts on entrance halls have set forth a few points to keep in mind as you decorate them. Since entrance hall convenience features are geared around removal and storage of wraps and outerwear, these are basic items that you will probably need:

* A place to put coats and hats. A hall closet is the best answer, but if that is not available, attractive coat hooks or a freestanding clothes tree will do. Possibilities include a bentwood tree or a Victorian hall piece.

* A place to put mail, packages, or groceries. A small chest that can also store gloves, scarves, keys, etc. is ideal. A table is helpful. Even a narrow ''floating'' shelf attached to the wall is better than no surface at all.

* A chair, stool, or bench for removing boots. This can be tucked under the table or shelf when not in use. If there are children, the hall should include a child-size chair, a waterproof shelf or cabinet for their boots, and a lower pole, rack, or row of hooks for their coats.

* A mirror, which is both decorative and functional. If there is no powder room at the entrance, most guests like a mirror for checking their hair and makeup before they move on to the living room.

* Floor covering that resists mud and water and is easy to clean, plus a mat outside the door to absorb some of the street dirt. A hard surface such as vinyl tile, marble, or slate is most resistant to wear and tear.

* Appropriate lighting. This is especially important if you choose to make your entry a small display gallery of paintings, graphics, and photographs, or if you want to highlight a few fine pieces of furniture. A new fixture with increased wattage or track lighting from the ceiling could be solutions.

Some experts like the idea of using dramatic and forceful patterns and colors in the entrance hall, since it is not an area where people linger. They offer reminders, however, that the mood and colors of any foyer or hall scheme should harmonize with those in adjoining rooms.