Lighter fare. Fresh seasonal fruits and vegetables. Subtle ethnic twists. Buffet-style. Elegant but not stiffly formal.

Forget the chopped liver swans. How about kosher dim sum?

These are some of the trends caterers say distinguish contemporary entertaining from years past.

Whether planning a bar or bat mitzvah, wedding or large gathering of friends, party-givers are asserting themselves more and showing surprising savvy, according to a sampling of Bay Area party planners and caterers.

"You have to make an interesting, varied menu," says Wendy Kleckner of Too Caterers in Menlo Park. "People are picky, and they have decidedly more sophisticated palates. They're reading [about food]. They're eating out more."

They want lighter sauces, a little more spice, less red meat and a lot more vegetarian — sometimes even vegan. "There's a big push on very creative vegetarian menus," Kleckner finds. "We use more Oriental [style foods], grains, seaweeds and grasses."

Low-fat options are commonly requested. "Even bar and bat mitzvah kids will ask for it," Kleckner says. It is not unusual, either, to have requests for nonfat fare.

In addition, clients are as particular about presentation as taste. People like "painted plates" with drizzled sauces, fruit purees and melted chocolates. They want stylized foods. And they enjoy three-dimensional designs.

"It used to be that food was presented in a much more horizontal manner," Kleckner adds. "Now it's gotten height."

Allison Rodman of Event Experts in San Francisco says: "People are very conscious of presentation. It's an important statement about you. This is a very competitive environment, not only work-wise but socially. A lot of people don't feel comfortable just slapping [a party] together. They want to put a certain glossy finish on it."

Yet, while demanding high-quality, stylish food, people tend not to want their parties to be too formal, says Steve Nichol of Red Robin Caterers in Marin. Dinner parties are "much more casual" than they used to be. For example, it's perfectly acceptable nowadays to mix china plates and flatware with colored paper napkins.

And for serving pieces, people are far more willing to accept woods, brass, even tortoise-shell, rather than the old, standard silver on ivory or white-colored tablecloth. Buffets are in favor.

"It's a trend away from the formality of the sit-down dinner," says Rodman. "People like a form that is more inclusive, more interactive between people. And that means a buffet."

Clients' high expectations require service providers to be on their toes, especially in the highly competitive Bay Area catering scene. But this has its pluses: people are open to new ideas and bold new tastes. Which allows caterers to let their creative juices flow.

This is true even with kosher cuisine. However, caterers must walk a fine line between honoring tradition and strict laws, while also being up-to-date.

In other words, chopped liver, knishes and kasha varnishkes have sentimental appeal, but today border on passé.

Red Robin's Nichol prefers using ethnic recipes, or variations on a theme. Why stick to traditional latkes, for example, when you can savor sweet potato latkes, or guiltlessly indulge in low-fat latkes?

"There's no reason that kosher has to be any different than non-kosher," in terms of menu options, suggests Kleck-ner. "You can do dim sum that'll be kosher, and fun. It's how you present it.

"To me that is a great challenge. I love it!"