If the student has been assigned a thesis topic or question, this is the place to start. If he has been instructed to choose his own topic, he should think about the idea he wants to address, for example, "recycling."
With a basic topic in mind, the student needs to narrow it down. Indiana University's Writing Tutorial Services suggests a few questions to think about. What audience is the student writing for? What does he want to accomplish with his essay? What aspect of his topic is he most interested in? With these questions in mind, he can make his general topic more precise. "Recycling" can become "how much energy it takes to recycle plastic."
An essential aspect of any thesis statement is the argument it presents. The student needs to take a clear stance on the topic he has raised, while still acknowledging that there is another side to the issue. His essay will explore and defend his argument. Thus, "how much energy it takes to recycle plastic" turns into "While recycling plastic is better than throwing it away, the process still consumes a lot of energy; therefore we need to develop more efficient ways of recycling plastic."
After writing his thesis statement, the student should double-check that it meets all the requirements for a good thesis statement. The education website Bright Hub recommends the following questions: Is the statement clear and concise with only one main idea? Does it take a strong stance on the subject, while acknowledging the other side of the argument? Does it answer a question? Does the argument presented use unbiased language and can it be backed up with solid evidence?