Should I major in a "hot" field so I know I can get a good job after I graduate?
No, it is better to major in an academic field that interests you rather than trying to make yourself adapt to a growing career field. The job market changes frequently; the "hot" fields today may not be the "hot fields" five years from now. Labor market trends do matter when making career choices, but it is better to consider trends after you have narrowed your own interest areas. In other words, don't begin your career decision-making process with what's available, begin with what you would enjoy doing. Also, it is very difficult to predict with any degree of accuracy what the job market will actually be like in the next five years.