When written first, an introduction is often uncertain, vague and unconvincing; but once you know exactly what you are introducing, it will be easier to manage.
In the introduction, you tell your reader exactly what he or she can expect to find in the body of your essay. Think of the introduction as a kind of contract with your reader.
Provide enough context (who, what, when, etc.) so that your reader will understand your thesis statement – the idea that organizes and supports the essay.
The thesis statement and your summary conclusion should be very similar. The thesis statement should be expressed in one, possibly two, sentences. It should state not only your topic, but also your position with respect to that topic – the position or idea that is developed in the essay.
A thesis statement will be easier to write at this stage because you now know where you’ve ended up in your exploration – what you “tried” or “tested” and how it turned out. A much more certain preview of your essay can be provided if you write or revise your introduction and thesis after reaching your conclusions.