My advice would be to keep your thesis statement as clear and easy to understand as possible. Try to not use long, complicated sentences. Try not to use unusual, "fancy" words. Be as straightforward and emphatic as possible. You may even want to restate your thesis, using different words, after you have stated it the first time. In other words, don't leave your reader with any doubts or questions about exactly what you will be trying to prove. Don't try to be "eloquent"; simply try to be clear.
First you might want to brain storm some ideas about your topic. Then, you will want to consider what type of evidence you will give to support this idea. Your thesis statement should be concise but encompass the idea you wish to prove. The key word is prove. The rest of your paper will be dedicated to supporting details and factual evidence proving your thesis statement. The statement should be an idea or theory about your given topic that can be justified or proved.
Prepare your support by considering what topics may be given to you. Creating hypothetical questions for yourself, such as What if I am asked to_______will help you seek passages and supporting details that can help you form a thesis which is supportable. In this way, you can create a concrete thesis statement.
Much like preparing for many things in life--job interviews, loan applications, etc.--a person should try to anticipate what will be asked of him/her in order to have the "ammunition" that is needed to succeed.
One of the biggest issues I have with thesis statements written by students is that many of them are vague and/or unclear. Your thesis statement should be specific and concise. Your thesis statement should not contain lengthy explanations, it should just clearly state the main position on the issue.
Typical vague thesis: There were many reason why Native Americans were conquered by Europeans.
Better, more specific thesis: Native tribes in the Americas from the Aztecs to the Seminole, Cherokee and Sioux were conquered by settlers from Spain and England because small pox greatly weakened their numbers, Natives did not possess modern weaponry, and they failed to work together to defend against European encroachment.
I can explain all of these main points as the main paragraphs of my essay, but now I have answered the question directly, and given my readers a specific idea of what I am going to argue, and in only one sentence.
A good thesis statement should also be analyticial. This means that it should include a reference to the arguments that you will be making in support of it. This spells out your argument in a convincing way and demonstrates from the beginning that you have adequate support for your argument. For example:
"This essay will argue that A is true, because of X, Y, and Z."
Point A would be your main argument, and X, Y, and Z are your supporting arguments. When a reader has to plow through a number of essays, they generally appreciate it if you spell out the thesis as explicitly as possible. In fact, it is a requirement for a very good score on many AP essay rubrics. It is also important, as #4 has suggested, to address the other side to your argument. This does not necessarily weaken your argument. Rather it demonstrates that you appreciate the complexity of the issue you are talking about in your paper.
Here are few pointers that should help. A thesis statement is debatable. If it is not debatable, then it is not a good thesis statement. For example, you might want to argue that technology is detrimental to people. This statement is debatable as not all people will agree with you. In addition, the best thesis statements also have a good supporting arguments. Finally, if you can address some potential criticisms to your thesis, then your paper can be even more successful.
Yes, the most important thing about creating a thesis statement is that you take a stance on whatever issue you are going to argue about. Often you will be presented with an article about a certain theme or an issue and be asked to respond to it. You will either have to agree or disagree with the thoughts expressed in that article, or take a qualified approach (where you agree to some parts and disagree with others.) Your thesis statement is a short, succinct statement of what you are going to prove.
A thesis statement is the key sentence (or 2) of the introduction to an argumentative essay. It clearly establishes what you plan to prove in the essay that will follow. If you know you will be writing about a piece of literature, you could review the work and brainstorm a list of interesting themes presented in the work which could then be a part of your thesis. If you writing about an historical topic, you could review the key causes and effects of the event and then argue something related to that. No matter what the task, it is important that you take a side -- something arguable.