Your thesis should express the main idea of your paper without listing all of your reasons or outline your entire paper. It should be a simple statement, rather than a list of support; that’s what the rest of your paper is for!
Whenever possible, look for peer-reviewed empirical research. These are articles or books written by experts in your field of interest, whose work has been read and vouched for by other experts in the same field. These can be found in scientific journals or via an online search.
If you are writing a research paper for a class, consider the other students. Is it likely that they will also be writing about your topic? How can you keep your paper unique and interesting if everyone is writing about the same thing?
Most research papers begin with a thesis statement at the end of an introductory paragraph. Even if it’s not a requirement, it’s a good idea to write a thesis statement as you begin to organize your research. Writing the thesis statement first is helpful because every argument or point you make in your paper should support this central idea you’re putting forward.