Early in the term, I have my students tell me what a thesis statement looks like. I break them up into groups and have them hash out a few bullet points listing the non-negotiable components of the ideal thesis. Then, I tell them to come up with a metaphor that best encapsulates their carefully considered components, but more importantly, what they believe the function of a thesis to be. Finally, I ask them why that metaphor was chosen. It’s a relatively quick exercise (no more than 3-4 minutes of group collaboration, and another 10-15 of class discussion) and I encourage creativity in the metaphors.
I wish I was far more fastidious over the years in copying down my students’ examples. Nevertheless, (digitally) scribbled in my lesson plan notes are the following handful of suggestions:
A thesis is like a compass (because it gives direction), blueprint (provides an overview), billboards (works like advertising), food label (lists contents), skeleton (provides general shape), receipt (tells you what you got), shopping list (tells you what to look for), bridge (brings you to a new place of understanding), flashlight (tells you where you are going and is “flashy”), treasure chest (holds all the “valuables”), heart (vital organ, the core), pyramid (strong foundation; made of blocks/components), magnifying lens (it focuses), spine (directs the body [paragraphs]), recipe (provides instruction), Tinder profile (makes people interested).
In any individual class the group suggestions are usually diverse enough to point out that no single metaphor can likely characterize all of the functions of a thesis statement. That is why I like this exercise, choosing a metaphors is an argument; students have to come to some consensus on which aspect is the most important, which is memorialized in their metaphor.
Taken together, these metaphors suggest a thesis statement provides direction and cues to the organization and method of a paper. Furthermore, it should be focused (or relatively concise) and bring the reader to a new understanding of a topic. Ideally, as thesis should be, er, “attractive” (compelling or interesting).
I prefer starting class discussions on the function of thesis statement rather than on the forms (the bullet point check lists). In the language of genre analysis, we are looking for the rhetorical purpose, not the conventions. I prefer this because many students have been drilled in the conventions; a thesis is one sentence; a thesis needs to provide three points of support; a thesis is the last sentence of an introduction. These are all guidelines, not hard-and-fast rules. Having a clear understanding of what the thesis is supposed to do can provide better direction of what it is supposed to look like. I would say the description above provides a good foundation for a generalized thesis.
But a thesis can do more, much more in fact, depending on the writing genre it is used in. Generally, I focus on argumentative/persuasive essays (but expository essays are common in my religious studies discipline), and thus a thesis in this context should also make a claim or take a stand, an aspect not clearly articulated in the above metaphors. In other words, you should imagine a reasonable person raising possible objections to your claim. This has two purposes. First, it draws in the skeptical reader who wants to see how you defend your claim. Second, it makes you a more thoughtful writer since it asks you to imagine, and possibly mitigate, potential counterarguments.
Often, another aspect of a strong thesis is that is passes the “So What?” Test, meaning that a person’s first thought after reading the thesis should not be, meh, so what? To me, this is a very complex issue because it relates to significance. Often, scholarly theses, understandably, do not pass the “So What?” Test for students because they do not understand the broader disciplinary issues the scholar is tackling. The significance can be presumed in this kind of writing (though good, effective scholarship should make significance explicit).
For students, I’ve found success in enlivening their thesis claims by having them clearly articulate the question they are asking. Among all the other things we’ve talked about, a thesis is a response to a question (and a conclusion based on premises). I’ve often found that a dead-on-arrival thesis is based on a rather uninspired research question. Instead of working on the thesis, I’ve had better responses talking to students about the questions they, often implicitly, are asking. While writing can be tortuous (and sometimes torturous), I suggest students return frequently to their question and try to refine it in terms of the new evidence they gather. In some situations, students find that the significance of their thesis can be rhetorically heighted by explicitly working their research question into their paper (according to the rhetorical principle of anthypophora).
Overall, I’ve found that defining the principle elements of a thesis statement can elicit deeply personal reactions. This may be due to personal preferences, misunderstanding regarding the genre of essay, or even disciplinary norms. These can be mitigated if we just tell our students, as clearly as we can, what we want a thesis to look like…and what we want it to do.
 I have had colleagues use “starter formulas” for creating thesis statements, such as: Primary Sources + Observations = Conclusion or Evidence + Claim = Conclusion. In these cases, the Observation or Claim should change the understanding of the underlying evidence. Elsewhere, I have seen more specific directives to fill in the blanks: While critics argue_____, I argue_____, because_____./By looking at_____, I argue that_____, which is important because_____./The text, _____, defines _____as_____, in order to argue_____. I think these are all reasonable ways to jump start students who are struggling, but I would also be careful of pigeonholing student creativity or artificially limiting their argument styles. I’ve also seen formulas that
 The advice available online for how to craft a thesis statement is absolutely daunting. It behooves us as instructors to help student navigate these resources if they have more questions. Arguably, one of the best online resources is the Perdue Online Writing Lab (Perdue OWL), but I would not say their thesis discussion is all that robust (a claim which pains me because it is such a valuable resource overall). I like the Harvard College Writing Center site because it provides some thesis caveats, and the University of Toronto Writing Support site because it talks about some myths. In addition to these, there are plenty of online materials which describe the process of developing a strong thesis, such as the University of Wisconsin Writing Center. I used the handout from Vanderbilt University Writing Studio to develop my own worksheet for the thesis drafting process. Finally, for fun, if my student are having problems with crafting a draft thesis, I tell them to go here http://www.wonder-tonic.com/filmthesis/.
 I have a friend who likes to tell a story of his college writing instructor who made all students develop their theses (claims) until no one in the class agreed with the claim. Your job, now, was to convince them otherwise.