There’s a lot of home decorating advice out there on how to create the perfect kitchen. But what goes into designing a truly great dining room?   As the holiday entertaining season approaches, it’s worth re-examining the dining area. In homes that have formal dining rooms, they often serve double-duty as homework headquarters, libraries or home offices. These rooms are a decorating challenge, especially if they’re directly in view of the front door.   Here, three interior design experts offer ideas on designing dining rooms that mix serious style with smooth function, and encourage holiday guests to linger over a memorable meal.   ___   IT’S ABOUT THE CHAIRS   We notice dramatic dining tables and beautiful tableware. But if the goal is to have long, lovely meals, comfortable chairs are vital.   High-end custom dining chairs can be expensive, says Los Angeles interior designer Betsy Burnham. Prices can easily climb above $800 per chair even before you choose upholstery fabric. But they are made for comfort and meant to last a lifetime.   Some homeowners opt for less expensive chairs from online sites like Overstock.com, and customize them with better fabrics. This can achieve a great look. But for comfort, Burnham recommends trying out dining chairs in person. Visit stores and showrooms, she says, and ask yourself: Is someone going to want to sit here for three or four hours and enjoy a great meal in my home?   “You want them to want to linger,” she says.   Comfort means different things to different people, of course.   “My least favorite thing is sitting down in a metal dining chair,” says interior designer Jaclyn Joslin, founder of the retail store Coveted Home in Kansas City. “It’s always cold and hard.”   You can also get creative with seating. Joslin has an upholstered loveseat along one side of her dining table, and she says that’s perfect at the holidays: “You can pile the kids on there.”   And consider adding seating for other purposes, like reading, if the room is large enough. In the Midwest, Joslin says, many homes have a large dining room and also plenty of dining space in the kitchen. So she encourages clients to add a few larger, upholstered chairs to give the dining room a second identity.   ___   CREATIVE RISKS   Dining rooms that aren’t used every day can be the perfect spot to take decorating risks.   “Frequently, clients will say OK to wallpaper in dining rooms, and that’s a bit of a departure,” Burnham says. “They’re afraid to wallpaper a space they’re in all the time because what if they get tired of it? What if it’s overwhelming?”   It’s also a great room for incorporating family heirlooms, perhaps with a style update, says interior designer Abbe Fenimore, founder of Studio Ten 25 in Dallas. If you have a sideboard or hutch that belonged to a family member, what better place to display it than where you’ll have relatives over for family dinners? These pieces are also great for displaying inherited serving dishes or other keepsakes.   Creative storage can make your dining room more beautiful, and offer space for things like table linens and holiday serving pieces. Joslin recommends including pieces that offer a mix of glass-fronted display space and closed storage.   And Fenimore suggests including a large-scale piece of art on one wall.   ___   LOVELIEST LIGHTING   “Everybody wants to look good around a dining table, so you want the right amount of ambient light,” Burnham says.   Ideally, you can mix can lighting embedded in the ceiling with a hanging fixture above the table, and then sconces and perhaps a table lamp if there’s room.   “If there’s the opportunity for a sideboard,” she says, adding a mirror and two lamps will create beautiful, warm light in any dining room.   All three designers agree: Use dimmers for flattering light at any time of day. “People like it dim,” Burnham says, “but not so dim that they can’t see their plate.”   ___   TO RUG OR NOT TO RUG   It’s a subject of debate among designers: Some people see a dining room as unfinished if there’s no rug under the table. Others see a dining-room rug as more of a challenge than a benefit — especially if the home has children.   “If you have kids who are out of the house, it’s a luxury. Get a gorgeous rug,” says Burnham. But if you’re focusing your decorating budget on other items, know that nicely polished floors can anchor a dining room on their own.   Joslin sees this logic, yet she’s found some homes where a rug is the perfect addition. If you use your dining room more for work or relaxing than for eating (and if you don’t have little kids eating messy food at your dining table), then a rug carries little risk and lots of potential reward.   A rug, she says, “definitely helps create that cozy, comfortable atmosphere.”