Decorators say most dining rooms are boring because all of the chairs match. Swapping out one or two with chairs of a similar design and contrasting colors will make the room more inviting. 
	You want variety but compatibility. You wouldn't want to add a chair with metal legs to a set that's made of wood. Find styles that have a common element but are different.
	New York designer Benjamin Noriega-Ortiz, quoted in The Wall Street Journal recommends using one color or material or a single style with a different color for each chair. 
	Keep the seat heights the same (about 18 inches) and make sure the back heights don't vary by more than 2 inches. As long as backs roughly line up, the grouping will look harmonious. 
	Using the same fabric for seat cushions, or even chair pads, is one way to achieve conflict resolution. 
	In a large dining room, place two chairs against a wall, perhaps flanking a buffet. To coordinate living and dining areas, surround a small expandable table with two seats and pull up others as they are needed.