It is best to begin thinking about a thesis topic as soon as you enter a master's or doctoral program; though it may be challenging without having done much coursework yet, it is best to keep the idea at least in the back of your mind. Then, narrow down your ideas and choose a thesis topic based on what you are passionate about, and what you have chosen to focus on throughout your studies. Consulting academic advisors throughout the process of choosing a topic can be very helpful as well.
Because a thesis takes an extensive amount of work and research to complete, it is absolutely necessary to choose a thesis topic that you are very interested in and are passionate about. While you are choosing a thesis topic, consider the courses you have taken throughout your education, and which ones in particular interested you the most. You might also go back over papers or other research projects you have completed, to see if the topic can be modified or expanded into a complete thesis.
It is important to choose a topic that is neither too narrow nor too broad. For this reason, your topic may go through an evolution process as you progress in your education, and learn more about your field of study. Meeting regularly with academic advisors can help you to target your studies as well as hone in on what you want your thesis topic to be; they may also be able to advise you on making your topic more specific in order to make it more likely to be accepted.
Thesis topics are virtually limitless in possibility. It is best to have a creative thesis; it may be an in-depth examination of a certain genre of literature, for instance, or it may be an idea for a new type of psychological treatment. A thesis should be personal, and particularly if it is a master's thesis, it can serve as both practice and a stepping stone for a Ph.D. thesis, which is considerably more difficult. No matter what the thesis topic is, it will take an extensive amount of research; typically, it takes much less time to actually write the thesis than it does to research it.
Of course, graduate schools are not the only places where a thesis might be required. Some high schools or undergraduate schools require students to create a type of senior thesis before graduating. This type of thesis is generally slightly less research intensive, and is based more on the classes the student took. Often, this type of thesis topic may be chosen based on a personal interest that can be applied to one's studies.