Because a thesis is in many ways the defining work of your master's education, the topic should reflect the expertise you've gained in the field and the many hours you've spent learning. Find a topic within your degree field that you're passionate or curious about. Do some cursory research into the topic, using your background knowledge to sort through ideas. Once you have a list of possible topics and angles, research previous theses and other published research and attempt to find out if an original angle is available.
Most thesis programs require an adviser or give you an opportunity to consult with one. In New York University's Draper Program, for example, you can choose among faculty members for an adviser but are not required to have one. Advisers provide guidance, pointing you in proper directions and helping refine ideas. Many students choose former professors for their advisers, as their acumen is considered trustworthy.
A thesis often begins with an abstract and an outline, as well as a beginning citations or bibliography page. These provide a framework for your paper. Once finalized, writing can begin. Strong theses often have strong abstracts or thesis statements that provide the skeletal argument that you'll fill in with the rest of the paper. The paper can be divided into parts or chapters and should end with a strong conclusion that summarizes the central points of the paper.
A well-researched thesis can be broken down into three research phases: initial, main and follow-up. The initial phase will consist of broad research, as you attempt to define the problem and solution. The core or main research will consist of an analysis of the identified problems, observations, empirical data and solutions, while the follow-up is a verification of facts and arguments that have been synthesized from your research. A large pool of sources will give you the strongest paper, though only a few can support the central aspects of your argument. Often, research will require you to communicate with individuals, either to corroborate data or as original sourcing. Studying for a thesis requires vast amounts of time.