Your thesis statement is a clear statement of your position and will typically occur in the first paragraph of your essay. The purpose of your thesis statement is to guide your readers by announcing the main claim of your paper. Most commonly, your thesis statement is the last one or two sentences in the first paragraph of your essay. However, some professors and assignments may require it as the first sentence in your paper, while others may want the statement at the end very end of your essay. Always check with your professor and the assignment details.
Sample thesis statements:
For an expository essay:
For an argumentative essay:
Here are characteristics of a good thesis statement:
It asserts your argument/view/position on your topic.
It establishes to whom and/or what your essay applies (scope of your essay).
It should focus on a specific aspect of your topic. Try narrowing down your topic if it is too broad.
It provides a guide of the main points and arguments in your essay.
It is debatable. It is possible to disagree with your thesis statement. 
 An exception to this rule is expository essays. These essays present facts to explain a concept, so they cannot be debatable.
As mentioned, your thesis should be arguable. For example, do not state a fact, such as “Sheridan College has a Tutoring Centre.” Include your main points in the thesis sentence. Make sure the thesis is neither too broad, nor too narrow.