The most common way to get to Los Angeles, is by way of the Los Angeles International Airport (LAX) which serves as a portal/gateway between the United States and the Pacific, South America and Asia. There are other airports in Long Beach, Burbank and Ontario (inland, about 40 miles east of downtown).
Also, LA is served by train via Amtrak and Metrolink.
Los Angeles is also home to a fantastic seaport which, through vaerious companies, offers cruises between the west coast, Mexico, Hawaii, Catalina Island, and other exciting ports of call.
Santa Monica on LA's exciting and trendy Westside, has long been known as the point where Route 66 hits the ocean, though I'm not sure if the route in this part of town is still in existance.