The body of the essay
If you have managed to produce a good essay plan, the essay will almost write itself! Each of your main points will become the basis for one of the paragraphs in the 'body' or 'development' section of the essay.
A common way of structuring paragraphs is to start by writing down the main point that you are trying to make and then expanding on it or elaborating it in four or five sentences. As you read other people's work notice how authors structure their paragraphs to get some further ideas.
Now that the majority of people use word processors, there is a tendency for paragraphs to become very disjointed. In some cases it is clear that the author has done so much cutting and pasting that their argument no longer follows a clear linear path. In your essay, adjacent paragraphs should be explicitly related to one another in more than a spatial sense.
One way of achieving this involves making a paragraph's opening sentence follow on from the theme of the preceding paragraph, using expressions like `However, further studies...'; `An equally important point/issue...'; `We need also to consider...'; etc.
Alternatively, it is sometimes effective to start a paragraph, or to end its predecessor, with a question. For example, `Might rising divorce rates be a result of changing legislation?' explicitly licences you to go on and discuss changing legislation.
When you are beginning to try out these kinds of techniques, don't be afraid to be blatant or clumsy in designing your structuring and linking phrases. Too explicit is always better than opaque. With practice, and an eye to the many good examples you will encounter in your reading, your style should soon become smoother so that the `joins' in your essay show less.