Almost all flights land at Los Angeles International Airport, LAX, which is located right in downtown near the coast. Shuttles run between the airport and other areas of the city, and cost $15-25 depending on destination. Taxis are available and will cost $20-40. A shuttle also runs to the nearest public transit hub.
Be prepared to rent a car. Public transit costs less, but usually takes twice as long as driving. Traffic in Los Angeles is infamously bad, but it is still just about the best way to get around.
Subway and bus lines service most areas of the city and cost $1.25 per ride. Maps and schedules are available from the Metro website
Taxis are used less in Los Angeles than just about any other large city in the US. Except where there are taxi stands, such as at the airport, taxis must be called by phone.