The main tactic to writing good thesis statements for papers about literature is having a thesis. A thesis is some basic argument or claim you will be supporting in the paper. Once you know what you are claiming and what sort of evidence you will be using to develop your claim, you develop a short "thesis statement" summarizing your thesis. This means that the best time to complete your thesis statement is after you have done most of your research and prepared an extended outline for your paper.
What makes a thesis good is that it is a claim for which you have solid evidence but which is not obvious from the text. Claiming, for example, that Lady Macbeth helps persuade her husband to kill Duncan is not a good thesis because it it obviously true. Arguing that Charlotte Lucas' viewpoint of marriage is actually more realistic and more likely to produce lasting happiness than than that of Elizabeth is a much better thesis as it is not obvious but can be supported from textual and historical evidence.
Finally, a good thesis should be narrow enough that it can be thoroughly research and covered in the paper. Making a claim about the roles of women in the Victorian novel, for example, is too broad; you are unlikely to have read all 40,000 odd Victorian novels, and are certain unlikely to even list their names much less discuss them in a single term paper. On the other hand, you could focus on the role of younger sisters in the novels or one or two Victorian writers.
When you travel to a new place, you often use a map or a GPS system to help you reach your location. A thesis is the road map to a paper's goal. It is a necessary part of a well organized paper that helps you write it and helps your reader read it.
How do you create a thesis statement? It is not hard but it takes some thought. When a paper is assigned, most people jump to a topic and an idea about that goal forms, but this is only a jumping off place. Research your topic, take notes, and think about what you have discovered. Has it changed anything about your original idea? Often it has.
Try writing what you want to write about in a single sentence.Keep it simple. Is it just right. If not, try again. For example the thesis for this discussion could be: a thesis statement is a sentence that defines the paper. But is that what this discussion actually doing? No. A better thesis might be: there are several steps to writing a good thesis statement.
Once you have a general idea and written a sentence that expresses it, refining the thesis into a strong statement is fairly easy. First remember to keep it simple and that means one central idea. So use a simple sentence or a complex sentence (this means a main and a subordinate clause). A compound sentence that expresses two ideas is not a good choice for a paper.
Examples of good thesis statements are:
1. Romeo and Juliet stories exist even today.
2. Since it deals with a conflict of families, Romeo and Juliet is an eternal tale.
Or if you want to, you can do a mini outline of the paper in your statement as in:
3. Romeo and Juliet has three elements for the audience: a love story, a strong conflict, and comedic scenes.
Writing a good thesis statement is not difficult but it requires thought and revision until it contains the framework(road map) that guides your writing and your reader's reading.