No. 9: Daniel Rothenberg

Firm: UBS

AUM: $1.56 billion

Location: Los Angeles

Age: 31

Note: This profile is part of a special series devoted to On Wall Street’s Top 40 Under 40 ranking for 2012. Every day we take a look at an advisor who made the list to find out the secrets of their success.

Daniel Rothenberg's entry into the advisory industry was all about relationships. He teamed up with a family friend who he knew growing up, and leveraged his connections from a college internship to seal his big first retirement plan client.

And those relationships have continued. Rothenberg, who has made this list three times, has worked with his partner, Roger Stephens, for more than six years. Their team also includes four support staff members. And that first retirement plan client he landed has been with them for five years.

Rothenberg's team specializes in 401(k) plans, endowments, retirement plans for nonprofits and individuals. That focus allows him to delve into the "nerdy" economics he has loved studying since college. The team uses the investment analysis they do for both retirement plans and endowments to better assess other investments such as mutual funds for their individual clients, he says.

Clients, Rothenberg says, will be demanding more specialized advice. "People will want to be dealing with specialists, more so than generalists," Rothenberg says. That means he is often in the office before 6 a.m. to handle trades and stays well after market close either in the office or attending meetings. And Rothenberg says he still employs the lessons he learned from the financial crisis to his work with clients today.

"It taught me very quickly that this is really a very client-focused business and a very client service-oriented business," Rothenberg says, "and then when people and clients need things done or have questions or issues, that we drop everything to get that done as quickly as possible." When it comes to investing now, Rothenberg's team has been conservative because of the uncertain U.S. political climate. They now favor municipal  bonds.

When approached by aspiring advisors, Rothenberg tells them they need a team. "You really have to hustle and put everything you have into it and do your best to try to find somebody that has a good business that you're interested in that you could complement,” he says.