This article was published by McKinsey & Company in honor of the Skoll World Forum.

An election campaign is poor preparation for government. Of course, you need to win the arguments to convince people that you have the right vision for the country. But the first lesson you learn as a leader is that making the case for change is a whole lot easier than making change the case. Once you get into office you are expected to quickly understand and marshal the tools of government to improve your country. As prime minister of the United Kingdom, and from my work today with leaders from every continent, I have identified three essential lessons about how to deliver real change in government.

The first lesson is to prioritize ruthlessly. As a leader, everyone you meet is looking to convince you that their issues should be at the top of your to-do list. But if everything’s a priority, then nothing gets done. You need to pick a small number of priorities and maintain a laser-like focus on delivering them. In Rwanda, where my organization—the Africa Governance Initiative (AGI)—has been working since 2008, the country’s impressive development progress has been driven by tight prioritization, first on the alleviation of poverty and now on specific sector reforms to move the country toward middle-income status by 2020.

President Paul Kagame has identified four priority areas critical to driving the country toward this ambitious goal: agriculture, energy, investment, and mining. Success in each area has been defined by clear, tangible objectives. For instance, with energy, the target is to increase the number of households with access to electricity from 14 percent in 2011 to 60 percent by 2017. To support this process, the Rwandan government set up a program called the Strategic Capacity Building Initiative, which links central government to ministries that are responsible for implementing each of the four priorities. The program also pairs international experts with their Rwandan government counterparts to ensure that the necessary skills are transferred to Rwanda in a sustainable manner.

This leads me to my second point. This might seem blindingly obvious, but it is crucial nonetheless: People matter. For your top priorities, you need your top people—the ministers you can rely on to push through the necessary reforms. And in the bureaucracy, you should bring in people with the right skills for implementation. Traditional bureaucracies are built to advise, not to deliver change. So you need to shake them up by bringing in new skills and approaches, often from the private or volunteer sectors. As prime minister, I recruited people we knew had specific expertise at delivering particular reforms. For the same reason, my charity puts great emphasis on helping African governments attract the best talent from the international private sector and the global African diaspora.

My third lesson is that you need to build a proper system for implementation. While in office I quickly learned that if my government was going to deliver, I first had to change the system of government itself. This is why I set up the Prime Minister’s Delivery Unit (PMDU) to coordinate, manage, and monitor activity on our priorities across government. We achieved progress only on the toughest issues after this system was put in place, allowing reform to be driven and monitored from the center. Take hospital waiting lists, for example. When I entered office in 1997, Britons had to endure waits of up to a year and a half for hospital appointments. By prioritizing the problem and managing it through the PMDU, we were able to restructure the lines of responsibility for cutting waiting times, address bottlenecks when they arose, and ensure that I could intervene when the system went off track. By the time I left office, we had managed to get waiting times down from 18 months to 18 days.

Although elections don’t prepare you for leadership, the lessons of how to implement change are clear—and they apply everywhere. Over the last few years, through AGI, I have worked with numerous African leaders. I have also worked with leaders in Latin America, Central Asia, Southeast Asia, and the Gulf through my consultancy, the Government Advisory Practice. Wherever we have worked, one thing is clear: Citizens rightly expect government to deliver. They expect government to create opportunities for employment, provide high-quality health, education, and welfare services, and ensure safety and security. The solutions to these challenges look similar whether you’re in Beijing, London, Monrovia, or São Paulo. All governments should take heart from this widening pool of knowledge. We live in challenging times, but the challenges we face have never been more alike.

Editor's Note: This collection of articles is part of “The Art and Science of Delivery,” an anthology of essays published by McKinsey & Company in honor of the 10th Anniversary of the Skoll World Forum. It is the most recent installment of McKinsey's ongoing series, Voices on Society, which convenes leading thinkers on social topics. (Copyright (c) 2013 McKinsey & Company. All rights reserved. Reprinted by permission)