For Larry Richard, founder and principal consultant of LawyerBrain, millennial attorneys can be an expensive resource for many law firms. While it takes an average of around three-and-a-half years for an associate to earn enough revenue for a firm to pay for his or her own employment, most millennial attorneys tend to leave firms just after two years, he said.

So how do firms retain millennials for longer? While there can be many different solutions to this challenge, most go back to a few core demands: changing the firm's culture and providing an engaging and flexible work life.

At “The Newest Generation” session of Thomson Reuters' 22nd Annual Law Firm Leaders Forum in New York, Richard joined several law firm and employment professionals to discuss how firms can adapt to meet millennial expectations.

For his part, Richard listed four changes firms can make to better train the youngest generation of attorneys. The first is a providing autonomy, which he defined as giving associates choices and “a chance to have discretion in doing important things.”

The second is giving employees meaning and purpose, which Richard said often varies and depends on the type of work law firms give their associates.

Next is social connection—a pivotal change, Richard said, as humans are “wired to socialize,” and not all law firms encourage friendships or camaraderie.

The last is mastery or competence, which Richard defined as making sure employees can progress, not just up the firm hierarchy but mentally and in their own practice areas.

To be sure, cultural and work-related changes weren't always the biggest make-or-break perquisites for millennials. Claudia Grillo, managing director of recruitment and marketing at employment research company Vault.com, said that, before the 2008 recession, what mattered most to law firm applicants was a law firm's prestige, followed by compensation and the location of the firm.

But after the recession, “We've seen a big shift,” she noted. “Now, the biggest correlations to satisfaction are law firm culture, quality of work, career outlook, associate partner relations and informal training,” Grillo explained.

Some firms are taking such data to heart. David Greenwald, chairman of Fried, Frank, Harris, Shriver & Jacobson, noted that, to improve his firm's culture and promote social connections, “we built collaborations spaces, and we built a billiards room.”

In addition, “we also heard about millennials' desire for better work-life balance, so we updated our alternative work arrangement policy. If someone wants a more flexible work arrangement, they know what the rules are.”

What's more, the firm also expanded its parental leave policy to provide more time off and make sure employees are eased back into work upon return, as well as offering more training and development programs.

Greenwald's firm, however, is not alone in catering to its newest employees' needs. Laura Saklad, chief operations officer at Orrick, Herrington & Sutcliffe, noted that, when Orrick realized its millennial employees wanted regular feedback on their performance, they set about to make their managerial staff more communicative.

“We're training the lawyers on how to have these conversations that some of the associates really want,” she said, adding that the firm is also currently looking at deploying “some cool apps where you can give real-time feedback” to associates on their performance as well.