Firstly, a good thesis statement can be made worse by locating it in the wrong place. When placing your argument, avoid putting it in the middle of the paragraph or later in the paper. Make sure it’s either in the very beginning or ideally in the very end of your introductory paragraph. The second way to ensure your thesis statement is good is to be as clear and precise as possible. Refine your thesis as you refine your argument. During the writing process, you might add or remove some points. Make sure to include or exclude them. If it is a general assertion, that is one indication that it is not focused enough. Another tip I have for you is to make your writing as clear as possible. Remove vague words and avoid abstract notions. Unless you’re writing a technical paper, avoid using really specialized vocabulary (and on the contrary avoid colloquialisms).