Oven

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Turn Off the Oven Before 12 p.m.
Event planner and decorator Matthew David Hopkins lives by this rule when he's getting the food ready for any kind of gathering: Switch the oven off by noon. One obvious reason is that it keeps the house cooler; and, once the party's in full swing, even if guests are mainly outdoors, some are still bound to be inside—and bodies create heat. Aside from saving you, the host, from overheating, turning that oven off is also a safeguard to force you to have most of the food prep (roasting vegetables or baking a frittata, for example) done hours before the party begins. "Unless you're a caterer, your goal should not be to serve everything hot," Hopkins says. "Instead, put out great-tasting, room-temperature—or even cold—food."
Pitcher

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Throw Some Cucumbers (Or Lemons) In a Pitcher
When guests of event producer David Stark come to his home and spy a beautiful glass pitcher simply filled with ice water and floating slices of cucumber, their eyes light up. "Ooooh, what is that?" they ask, ever so impressed. Another no-brainer from Stark, whose new book is David Stark: The Art of the Party: Chill cubes or wedges of watermelon and squeeze some lime juice on top for a quick and refreshing appetizer or dessert. Insta-party snacks and drinks like these look special and elicit raves, Stark says, but are supereasy.
Watermelon

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Buy a Big Melon
Speaking of watermelon, Hopkins swears no guest at a summer party ever turns down a drink made with watermelon—whether alcoholic or not. He purees chunks of the fruit with a splash of citrus juice (lemon, lime or orange) and then mixes that with sparkling water; you could also go the margarita route and combine pureed watermelon with tequila and Triple Sec or turn the melon into a vodka martini.
Croquet

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Dust Off Your Croquet Set
Both Hopkins and Stark are huge fans of old-fashioned lawn games, including croquet, cornhole (a.k.a. beanbag toss), lawn bowling, horseshoes and badminton. "It's a way for people to have a little entertainment—a short departure from the party," Hopkins says. Stark also finds having these diversions can help get a gathering started and prompt people to meet each other.
Party lights

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Hit Up the Hardware Store
Even if you're the type of person who picks up a bunch of carnations, throws them in a vase and calls that decorating, you can create a Pinterest-worthy party space without stressing out. Stark recommends strings of old-fashioned light bulbs—you can get them at a hardware store or PartyLights.com—for creating "instant magic."
Blankets

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Outsmart the Things That Can End Your Party Too Early
Part of being a terrific host, says Stark, is anticipating guests' needs—which, at an outdoor summer party, can mean knowing that they're going to start scratching their ankles and swatting the backs of their necks as soon as the sun goes down. He puts out buckets of mosquito repellents so people can just help themselves. Stark also likes to prepare a basket of blankets or shawls in case partygoers start to feel chilly.

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