The concept of social engineering can be viewed on various scales which range from massive manipulations of whole societies, to interaction between two persons that results in a great social impact. But, regardless of the scale, social engineering involves actions which are manipulative in nature and which uses means that lead toward a definitive end goal of modifying the behavior of others.
On a large scale, examples of social engineering include using the full array of governmental, and interpersonal forces to change the publics attitudes and behaviors in personal hygiene, to convince the public to accept fluoridated water, and to create belief systems that favor getting vaccinations and taking action to enhance care and preservation of the environment. This can be classified as a many-to-many relationship that has an impact on all.
On a very small scale, when just one person acts to convince just one other person to release the most dangerous and highly coveted secure information, such as releasing the plans for nuclear weapons, can change the course of human history. This can be classified as a one-to-one relationship in social engineering that had a-one-to-all result.
On any scale, there are one-to-many relationships where one person convinces many people to change their views, beliefs and attitudes, with results that can change all history. The first African American president convinced many to vote for him. Jesus convinced many to follow the new systems of faith and belief that he preached and taught.
The tools of social engineering are any tools that work to get people to do what is desired. These tools can be criminal, unethical and immoral. False propaganda, "rabble rousing", and other forms of deceptive or outrageous speech and conduct can cause major events that affect massive numbers of people. The false claims about Jews in Germany led not only to public outrage, but to public acquiescence when the worst of abuses began, but when they could also have been stopped. Radio talk show hosts who call for assassination, but who stay just a bit back from the legal line, are frequently suspected of trying to get someone from among their audience to carry out the deed for them.
When commercial enterprises conduct social engineering in order to adapt people to using new technologies, we get whole new languages of shorthand for those who text and tweet. We get people who have adapted their jobs, work habits, and work methodologies to accommodate personal and portable computing devices. People make adaptations to the devices more often than the devices have adapted to the needs of people. But it is social engineering that convinces people to not only try out the devices, but to pay money in order to do it.
The tools of social engineering are plentiful. Advertising campaigns and news reports that tell the public to start washing their hands and taking other measures against the flu are examples of positive and necessary social engineering. Speeches, written material, film, music, televised content, radio content, art, and every other form of communication and expression goes a long way toward making social engineering a lot more rapid and the results more effective. But the results far more volatile, given the ability of opposing social engineers to use the same tools.