Here is some information regarding undeclared majors: http://admissions.ucdavis.edu/majors/undeclared.cfm
You will attend orientation based on the College of Letters and Sciences schedule. There you will be meet with an academic and peer advisor and will be given direction in which courses to take. You would be exploring majors within your college and mainly taking GE required classes and pre-req’s need to declare a major in that college.
Here is a link for the Majors/Minors available in the L&S college:
http://www.ls.ucdavis.edu/advising/majorminorlist.html
What was your original intended major? You can switch colleges after Fall quarter if you feel that you would rather pursue another area of study.