Talk to your parents and use net price calculators (or ask your parents to use them) on the web sites of the colleges you are interested in. Include some UCs and CSUs to check how affordable they will be for you and your family.
Start building a list of less difficult to get into colleges, unless you are happy with a backup option of starting at a community college (usually a good path in California to prepare for transfer to a UC or CSU, but may be less suitable if you will have already taken lots of college courses by the time you graduate from high school).