Explore Visitcalifornia.com. This official website has a plethora of information about travel tools and things to do in California. The site includes a free visitor's guide and an interactive map with which to plan your trip.
Once you have decided where you plan to visit in California, search online for a travel package that fits your budget and needs. If you are driving, visit Roadtripamerica.com for travel tips and route suggestions.
Research places you plan to visit. If it's Disneyland, for example, check out Disneylandvacationtips.com to get a heads up on the best time to plan your visit. For trips to Legoland, you can plan your visit at Californialegoland.com.