Texts are often divided into sections (just like books will be divided into chapters), and within each section, the text is then divided into paragraphs.
Whereas the introductory section of a text presents what will be discussed further on, the body and conclusion sections develop the ideas that were initially set out. In a traditional three-part essay, the sections of the body often have sub-headings to help readers orientate themselves within the text. An introductory part of each section will present what will be discussed in it and a brief concluding part will sum up what has been discussed before the text moves on to the next section. To some extent, each subsection of the text thus functions like a mini essay.
Writers following the IMRaD structure, will also divide their texts into sections; after the Introduction follows sections on method, results and a dioscussion section.
Structuring the section
Although most texts go through some kind of restructuring during the writing process, it is wise to aim at a logical and coherent structure from the start. To work with clearly recognisable parts of the text makes it easier to restructure the text if necessary.
Working with subheadings
One way of signposting the structure while writing is to insert tentative subheadings as soon as a new topic or turn of reasoning begins. Such subheadings help writers to see the structure of their developing texts and they also serve to clarify the pros and cons of the chosen structure.
Depending on instructions from supervisors or publishers, subheadings may have to be removed in the finished text. If this is the case, they can be transformed into suitable topic sentences or transitional phrases in order to help the reader make the desired transition from one section to another.
Division into paragraphs
Generally speaking, there should be one idea per paragraph. This means that when you move on to talk about something new, you should start a new paragraph. However, how often you start a new paragraph also depends on the type of text you are writing. Some genres accept very long paragraphs while others expect them to be fairly short. The writer's personal preferences and writing style may be of relevance here, although it is of course essential to follow disciplinary conventions and stipulated guidelines.
In any case, there are two ways of indicating the start of a new paragraph. Either you leave a blank line between paragraphs, or you indent the first line of a new paragraph. If you are student writing a paper, check the course stylesheet if there is one or ask your teacher for recommended format.
Remember that you divide your text into paragraphs using one of the methods explained above - you cannot combine them. Please be careful when using certain word processors, since they automatically insert extra space between paragraphs, whether you like it or not. Unless you can turn this automatic feature off, you cannot use indentation, since the two cannot be combined.