Well written introductory documentation starts by first understanding the purpose. The purpose of the document is to get the reader to become acquainted with whatever you’re trying to introduce. Not only that, but one should keep in mind what they wish to accomplish by introducing the topic. This would help organize the overall direction of the paper.
After you have a good understanding of what you’re trying to introduce, and what you hope to accomplish by introducing it, you can then start with the major topics. These major topics can then be broken down into smaller sub-topics, and those sub-topics into smaller sub-sub-topics.
Any and every topic should have an introduction and a conclusion. Sometimes, even be better to write out the introduction and conclusion first, and fill in the rest later. Having an introduction would save a person from re-learning information he is already aware of.
If the topics are absolutely independent, then you’ve written a referential document. Examples of referential documents are dictionaries, encyclopedias, and cook books. Each topic is independent of each other.
An introductory document progressively builds the reader’s understanding, and finally arrives at the original destination it intended.
Well written introductory documentation can aid a person who knows nothing about a topic into becoming well-informed of the topic. A referential documentation can aid a person who is well-informed of a topic in recalling things he has once learned. Understanding the difference between the two will be beneficial to any type of written communication efforts.