This is a great and important question. Citizens of a democracy, in order to maintain their rights, have duties to fulfill. Being informed, voting, participating in one's community, and ensuring that a good public education is available to all are the means of preserving these rights.
A good citizen is informed, about how a democracy works, about politicians running for office, the laws of the land, and the issues that affect the community, the region, and the country. Citizens should understand the country's constitution, which is the foundation of a democracy, setting forth everyone's rights and duties. I have carried a pocket copy in my purse for many years, since I frequently encounter people who misunderstand it or have never looked at it, so I can refer to it. A citizen who is not informed about how the country works cannot possibly be vigilant about seeing to it that the government does what it is supposed to do and does not do what it is not supposed to do. Being informed means doing research on candidates and issues. This includes looking at statistics for oneself, since these are often manipulated by politicians. We need to be informed about the records of the people running for office, not simply taking their word for what they say it is. One needs at least rudimentary scientific knowledge, so that one can examine evidence intelligently, on issues such as climate change or drinking water safety. A good citizen knows the laws and follows them. This is part of the social contract of a democracy, not that police have to enforce every little thing, but that people choose to willingly follow the law in exchange for the protections of a democracy and the harmony that this brings. A good citizen has knowledge of his or her own community, of his or her own region, and his or her own country as a whole, as well as some knowledge of other countries, since a democracy must interact with the rest of the world. You need to know what the problems and potential solutions are where you live. And if you think that Africa is a country, which it is not, you cannot possibly evaluate your country's relationship with it. A citizen who is not informed is, simply put, not a good citizen.
Citizens need to vote. In the United States, voter participation is disappointing low, a little over 53%. In Australia, voting is mandatory, and there is a fine for not voting. A democracy does not work very well if citizens don't vote. Citizens feel disenfranchised and are even less likely to participate in a democracy in other ways. In the United States, people died so we could all vote, first in the Revolutionary War, then for the African-American vote, and then for the vote for those under 21 years of age, after so many 18-year-olds died in the Vietnam War without even having a voice. Women fought hard for the right to vote, too. The entire point of a democracy is to have representation based upon the will of the people, so if people do not vote, democracy can lead to leadership that represents a small fraction of the populace, creating much dissatisfaction, which is detrimental to stability.
Participating in one's community goes a long way to creating a more successful democracy. Going to town meetings or school board meetings, joining a litter cleanup project, mentoring younger people in the neighborhood are all ways that we can participate in our communities. Our communities do a great deal for us, and this is a means of giving back or passing it forward. It is also a good way of staying informed of the issues and a good way of meeting one's local leaders. We are better citizens when we are active in our communities, and we make democracy better.
An educated populace is essential to a successful democracy. It is up to us to invest in good public education, which is the best means of ensuring that the democracy continues. People who are educated are going to be better citizens, pay more taxes, participate more fully in their communities, and be more likely to vote. People who are educated are more informed about the issues, more likely to make good choices in leaders, and more likely to challenge a democracy gone awry somehow. Good public education is a staple of a good democracy. This means true public schools, of the highest quality, for all students, not for-profit charters and private schools meant to prevent children from learning about evolution, not schools that are de facto segregated, with the least experienced teachers and shabby, out-of-date textbooks. In a democracy, everyone has a stake in good education, even those without children. People who are well-educated are better prepared to live in a democracy in which the rights of the "other" are respected. Public education is meant to expose us to people who are different from us, giving us different perspectives and teaching us respect and appreciation.
To ensure a properly functioning democracy may seem like a great deal of work, being informed, having to vote and participate, understanding a constitution and laws, spending money on education, even if one has no children. But I do believe that a constitutional democracy is the best form of government ever created, and no matter how much work it seems to be, the benefits are countless.