“Tis the season of somewhat-stressful party throwing. And right about now, it helps to know that even entertaining experts have had their own learning curves. Sisters Lauren Purcell and Anne Purcell Grissinger – authors of the recently published “Cocktail Parties, Straight Up!” (Wiley, $16.95) – moved to New York together in 1993. And though their ambition was to throw great cocktail parties, it took a while to make it happen.

Their first foray, a New Year’s bash in the Upper West Side two-bedroom they shared, was not exactly a smash. “The food tasted okay, the drinks flowed. But it never really jelled. Anne’s friends were on one side of the room, and my friends were on the other,” Ms. Purcell remembered.

Undaunted, the pair spent a Saturday at Barnes & Noble, combing the store for a no-frills guide to help them throw better parties. They came up empty handed. “We got a lot of ideas like ‘Staple sheets to the walls to create a tent look,'” Ms. Grissinger said. “Whimsical and creative – yes,” Ms. Purcell added. “But not so helpful for two girls on budgets with day jobs.”

Realizing they were on their own, the sisters began experimenting. Over the next 10 years, not only did they host countless parties in their Upper West Side apartment, they also took notes. “We kept a party notebook,” Ms. Purcell explained. “We’d write down who we invited, who came, what worked and what didn’t. We’ll look through it now and see names of old boyfriends and things like ‘Crab dip: huge hit.'”

Among the notes were tricks they used as conversation starters, like a map with little pins where guests could mark places they’d traveled to. “We aimed for things you could do or not do,” Ms. Purcell explained, “so nobody would feel uncomfortable.”

Just getting the parties started was a bit of work – at least in the beginning. “When we first started throwing parties in New York, the overwhelming response was, ‘Oh my God, I can’t believe you’re doing it in your apartment,'” Ms. Purcell, now a deputy editor at Self magazine, said.

“At the time, nobody was giving parties in their apartments,” Ms. Grissinger, a consultant for JPMorgan Chase, said. “People would just tell a bunch of their friends to meet up at a bar.”

But having grown up with parents who threw parties often, the sisters had a different style of entertaining in mind. “We wanted to create a place where people could have actual conversations,” Ms. Grissinger said.

As Ms. Purcell put it, “We had fantasies about people meeting at our parties and toasting us at their weddings.”

Gradually, the sisters became the kind of hostesses they envisioned, and more and more of their friends began calling them for last-minute party-throwing advice. When an editor friend asked them to write a piece on giving parties, the two came up with the idea of turning their party notebook into the party-throwing book they’d sought out years ago.

The result, “Cocktail Parties, Straight Up!” contains recipes and ideas for theme parties, but also the kind of “how much food for how many people”-type advice you’d ask a trusted girlfriend. Its tone is more Mary Tyler Moore practical than “Sex and the City” glam. Here you’ll get straightforward advice, information, and recipes. The pair suggests, for instance, a guests-to-seats ratio of three guests to every available seat or perching place: “When the majority of people are standing,” they write, “a party takes on a lovely, swirling atmosphere. Too many sitters and you’re back in dinner-party land.”

As for their own party-throwing, they may have become experts, but they still have goals. “We still haven’t caused any weddings,” Ms. Grissinger said.

A Mighty Big Drink

One of the best stress-busting party tricks in “Cocktail Parties, Straight Up!” is a throwback: serving signature cocktails by the pitcher. “Mixing up a batch of one fun drink ahead of time keeps you from being stuck behind the bar all night,” they write. “And letting the guests serve themselves – and anyone standing nearby – gives them still another opportunity to meet and mingle.”

Between the Sheets (makes about 20 drinks, or one pitcher):
2 1/2 cups brandy or cognac
2 1/2 cups triple sec
2 1/2 cups rum
2 1/2 cups fresh lemon juice

Combine all ingredients in a large pitcher, add ice, and stir for 30 seconds. Spoon out the ice cubes. Store the pitcher in the refrigerator until party time. Serve in martini glasses or short glasses over ice.