A thesis statement needs to provide the reader with two pieces of information: the topic of your report and the writer’s stance. Stance means your opinion, your approach, your position on the topic. This is especially important if you are writing any type of persuasive (argumentative) text.
The thesis statement should be short - usually only one sentence and rarely more than two.
The thesis statement appears in your introduction; usually at the end of the introduction.
You cannot write a good thesis statement unless you have a clear idea in your own mind about what you want to say. So make sure that you can write this down in simple language; it should be a single idea, not a list of random thoughts.
Once you have a good thesis statement you have a good basis for developing a plan for your essay or report.
To see how writing a good thesis statement can help you plan your essay see the Using a Thesis Statement to Plan an Essay page.