The Degree programs at Temple set out the specific requirements for majors at Temple in the Academic Programs section of the Undergraduate Bulletin and the "List of Degrees and Programs" and professional schools in the Graduate Bulletin.
Starting and changing an undergraduate major at Temple usually involves meeting with the advisors of the Schools & Colleges. Each School and College has official ways of going about this, usually explained on a page in the Bulletin with a title like "Academic Policies and Regulations" that is linked from the initial page for the Schools & Colleges. The process of changing majors is also known as Transfer Between Colleges in the University or Intra-University Transfer (IUT).
The Career Center strongly recommends you meet with a Career Coach if you are struggling with choosing a major or career. The Career Center has a program called Focus-2 (about half-way down the page) which is a self-paced tool that should enable you to self-assess your career relevant to your personal qualities. It also helps you explore career fields and major areas of study that are compatible with your assessment results. FOCUS does not tell you what to do; rather it provides some brainstorming ideas.
MyMajors.com List of college majors with information and descriptions
About.com College Majors and Your Personality Online quiz that tries to match your preferences with a major.
Reports to consider if you are looking at a major in terms of its job potential:
There are books in the Temple Libraries on what you might expect from college majors and what you might do with them for employment. The link is to a keyword search on the phrase "college majors" and leads to 10-12 books recent enough to still be relevant