There are always disasters facing someone each semester because files got accidentally erased.
Make backup copies often! Printouts (hardcopies) of drafts are often reassuring. When turning in a draft of one chapter of a thesis it is helpful to attach the full bibliography and an outline giving the titles and current status of the other chapters.
Instructors usually will return your term paper at the end of the semester. Theses, however, are retained by the Department. Make a second copy if you want to keep one for your own use.
Maintain a separate file of your bibliography. It can be easily updated as you find new sources and discard old ones. If you are reluctant to use modern technology, buy some 3″ x 5″ index cards to use for your bibliography. Every time you consult a new source, put the bibliographic information on a separate index card. When you are ready to prepare the bibliography, all you have to do is sort the cards alphabetically, and then type up the information.
Before submitting your paper make sure to check for some common mistakes. In particular, check all spelling, especially proper names and technical terms. Check all direct quotes to make sure they are correct both as to wording and spelling. Check all footnotes to guarantee they are numbered consecutively, and that all are included.