Rich Collier never feels like he has enough people -- or time -- to accomplish everything that needs to be done. "We have far more work than people," Collier says. As vice president of engineering at Etnus LLC, a software-debugging firm based in Natick, Massachusetts, Collier leads 24 people who work on 75 projects. Juggling projects is a day-to-day challenge -- and reality -- for Collier and other leaders.

As the economy continues to struggle to regain its footing, hiring freezes and limited resources can pose substantial barriers to success in firms that are understaffed. People are asked to take on more projects, to embrace additional responsibilities when colleagues change jobs -- or are laid off -- and to continuously reassess projects' priorities as funding is cut or reallocated.

How can we do more -- with less? How do business leaders manage multiple projects? How do team members keep track of the wide range of changing requirements and priorities so nothing slips through the cracks? To learn more about how to best manage multiple projects, Fast Company turned to the true experts, project leaders with a full plate -- who always go back for seconds.

Prioritize Productivity

Regardless of what approach you take, leaders agree that prioritization is the key to their success. Lori Nerenberg, a vice president of Chicago-based Northern Trust Corp., oversees 20 projects at a time. About half of those will be completed within six months. Nerenberg encourages her team to work on several projects at once to maximize production. "If we can work on the right number of projects concurrently but stage them in a way to optimize the use of shared resources such as analysts and programmers, we can get more done without overly taxing any one individual or group," she says.

Robert Treves sits on Demand Management Steering Committee at Seattle-based Getty Images. That committee reviews and approves projects pursued within the company. Each week, the committee considers project managers' proposals, ranks leaders' requests, and establishes teams' priorities. "We decide whether to put 15 people on one project or 10 people on both projects, which then takes longer for each to complete," Treves says.

As a project manager and team member, it's important to negotiate with your boss to determine your priorities, says Jim Hanlan, an assistant vice president at the health insurance firm CIGNA in Philadelphia. "The first time you are given more than one project, ask them what it means in terms of personal priority," he says. If the projects are equally important, ask whether you should divide your time evenly between them. If a project sponsor wants more of your attention, direct him to your boss for confirmation. "Sometimes, escalation is not a bad thing," Hanlan says. "You need to get clarification and find a default position."

Sometimes, such decisions aren't easily made. Mary Freese, a contract project manager based in Minneapolis, says she's often called on to play the role of arbitrator, working with departments that have conflicting priorities. Freese asks group leaders to make the case for their projects, explaining the business reasons that they need more resources. "You should get project justification upfront and push users to articulate that," Freese says. She peppers business owners with questions, such as how much money and time are needed -- and how a project is going to benefit the company. And if Freese thinks a certain project has a stronger business case, she'll suggest what should be prioritized.