In short, instead of merely stating a general fact or resorting to a simplistic pro/con statement, you must decide what it is you have to say.
Tips: Do not expect to come up with a fully formulated thesis statement before you have finished writing the paper.
Keep revising until the thesis reflects your real ideas.
Tip: The point you make in the paper should matter: Avoid formula and generic words.
To avoid misunderstandings, be as specific as possible.
Compare the original thesis (not specific and clear enough) with the revised version (much more specific and clear): The thesis statement should do more than merely announce the topic; it must reveal what position you will take in relation to that topic, how you plan to analyze/evaluate the subject or the issue.
Normally you will continue to refine your thesis as you revise your argument(s), so your thesis will evolve and gain definition as you obtain a better sense of where your argument is taking you.
Tip: Check your thesis: Your thesis should be limited to what can be accomplished in the specified number of pages.
It should present the topic of your paper and also make a comment about your position in relation to the topic.
Your thesis statement should tell your reader what the paper is about and also help guide your writing and keep your argument focused.