Traditionally, in the western world we are preferred to eat in room designed for eating in, while seated at a table. This may not be the case in the future of course since teenagers and younger children seem to prefer to eat from a plate on their laps whilst they sit on their bed, but hopefully by the time they become adults they will have grown out all such childish habits! What will help and encourage them to use a dining-room and set at a proper table on a proper chair, however, will be a well planned room! Let us look at the essentials.
Obviously space is a major influence on how you lay your dining-room out, as well as the size of your family; it would be no use having an oak table fit for a baronial hall if you have to pull in your tummy to squeeze past it! Equally, a tiny circular table will be no use if you have any large family so the first thing to do is to measure your dining-room, draw a rough plan of it and mark out the areas that you will need to reserve for such items as display cabinets or even, if the room is big enough, a home bar. You will then have a pretty good idea of the size of table that you can fit in. Do bear in mind however that although there may be just a small number of people who will usually use the table under normal circumstances, you may wish to have guests to dinner or even have a party with many people coming and going to collect food from a buffet so do think carefully about whether or not to go for an extending table; they cost more of course and reduce your choice of materials somewhat but you may well bless the decision to buy one in the future.
The materials that you pick for your table, subject to the caveat above, would of course is subject to your own tastes and home decor; the commonest material is of course a timber, occasionally solid but more often than not veneered (usually just as visually attractive as solid wood but much more stable and far less prone to warping), glass, plastics and even metals. You will probably want to pick an item of furniture which not only fits in with your decorative scheme but which is also easy to clean and maintain.
The next major choice of course is the chairs, and whilst again the choice is dependent upon your budget, personal taste and decor the number that you buy is often a difficult decision; when the numbers of diners fluctuate you may well be able to extend the table but you cannot produce additional shares out of thin air! In addition, manufacturers tend to produce matching chairs in batches, and if you buy anything other than the simplest and most popular wooden chairs you may have difficulty in the future in buying replacements or additional ones. Do bear in mind that if you buy simple wooden chairs you can always make them more comfortable and more decorative with purpose made cushions.