The arranging of the furniture in your dining room will make the difference between a spacious open feeling in the room which contributes to conversation as well as ease of movement while seating, serving, eating and relaxing.
The first rule is to give 30-36” of walkway between large furniture pieces. The minimum space between furniture pieces ought to be no less than 24”. Anything less than that is a crowded space in which both people and furniture has no breathing room.
Super important is the spatial relationship of the chairs to each other. I like to allow for 24” of width for each chair so people do not feel that they are eating in their neighbor’s lap and there is space for their place setting and elbows. A 48” round table usually seats 4 and a 60”can accommodate 6-8—obviously depending on how tight you want to be. You can also have the table “set” for 6 on a daily basis and if there are 8 people, add the last two chairs for that occasion so that your dining room looks and feels spacious when not in use.
If you are considering, and have the space for, a buffet or credenza, you would want it to be at least the height of your dining table or taller.