The program at your college is likely to have detailed rules for the completion and submission of a thesis. In addition to agreeing with your supervisor on subject matter and scope, you will be expected to prepare a manuscript according to detailed specifications. From day one, know what the finished product must look like: its length, the need for an abstract, rules for diagrams and illustrations, requirements for binding or extra copies and, above all, the deadline for submission.
It is usual for a program to require theses to be prepared in conformity with a designated style guide. Hopefully, the style designated will be one with which you are already familiar. If not, studying it closely before you start writing will save a lot of rewriting later. Common style guides are the Chicago Style Manual, the Modern Language Association (MLA) Handbook and the American Psychological Association (APA) Publication Manual.
Your supervisor will help you to understand how familiar you need to be with published work in your field of study. Almost every thesis requires what is called a "literature review" to demonstrate your command of relevant research already conducted on the topic in hand. Since this might require extensive reading, it is important to draw up a plan and make time to complete it.
Students preparing a thesis for the first time are often surprised at how time-consuming the task of providing references can be. Any statement supported by a citation will require a footnote conforming to the requirements of the designated style guide. It is essential to keep careful notes of quotations and page references while conducting research. Much time and energy is wasted trying to trace important passages in books or papers you last opened months ago.
In addition to footnotes, a bibliography will be required. At a minimum, this will set out details of the works cited in your footnotes. You may also be asked to provide a general bibliography of relevant background material, cited or not. Again, keeping accurate note of titles, authors, publishers, places and dates of publication while reading will save duplication of effort when preparing the final manuscript.
Schools will have different levels of tolerance for typographical and other errors in the submitted manuscript. It is wise to aim, at least, for perfection. Proofreading is another task requiring time and attention, and it should be factored into your preparation plan so that it can be completed before the deadline, and in advance of making any duplicate copies of the final manuscript.
Some schools may require an oral examination on the thesis, conducted either by internal or external examiners of both. Since time may elapse between final drafting and the examination, it is important to refresh your memory by rereading the thesis. If the identity of your examiners is known, it may also be possible to anticipate questions by looking at their publications and knowing what their main interests are.