How should I go about making CV as an undergraduate? I'm just an undergraduate math student, and I need to make a CV for a research application. However, from the CVs that I have already seen I have nowhere near enough to fill probably half of a page. I mean I can really only put my education history which is 3 schools. What else should I put?
Before starting research, An undergraduate student really only has a résumé. A curriculum vitae is generally intended for someone who is intending to pursue a career in research, and has a somewhat "standardized" format (although there are still many variations). 

But as a young student just beginning to do research, I would recommend that you focus on listing skills that you have that would make you appealing to someone interested in hiring you. If you have more than the standard training for someone at your level in university (more courses, have already done research projects, etc.), then you should list that information. Similarly, if you have special skills (programming languages, familiarity with specific techniques or tools, etc.), then those should also be listed. 

Any jobs that you've held that might also prepare you for such an experience would also be of interest.