Drive YourselfFor most people, the decision to drive your own car or rent a car in Los Angeles will be a no-brainer. Attractions can be far apart, and the public transportation system is inadequate and complicated if you're traveling any distance or crossing city lines, which is inevitable.
Driving rules and behavior are a little different in Los Angeles than other parts of the country, so before you arrive, check out my Tips for Driving in LA. They will save you some confusion and frustration.
To help you map your routes and navigate LA traffic, I've put together a comparison of the best online maps of Los Angeles with the pros and cons of each. Maps are your friend. Orient yourself before you go.
If you're flying in and need to rent a car in Los Angeles, use this Renting a Car in Los Angeles resource page to help you find the best deals. If you're into something a little more adventurous, you'll also find links for luxury car and motorcycle rentals.
Parking in Los AngelesKeep in mind when calculating rental car rates that most hotels in Los Angeles charge a nightly parking fee, which can range from $10 to $40 per night. The more expensive the hotel, the higher the parking fee. You'll also have to pay for parking at most attractions and most high-end restaurants. Streets in all commercial areas are metered, and many neighborhood streets near commercial areas require resident permits. So your parking expenses per day may be more than the total car rental rate for the day. "Motels" usually still have free parking, even in Hollywood.
Hire a DriverIf money is not an issue and you want to make sure you get where you need to be on time, you can hire a car and driver, or a driver to drive your car.
There are a variety of options for hiring chauffeur-driven cars or personal drivers in Los Angeles. I've summarized them in this page on Limousine and Driver Services in Los Angeles.
TaxisTaxi service has improved in Los Angeles in recent years since prohibitions on cruising taxis have been lifted. If your business in Los Angeles is primarily in Downtown Los Angeles or within the Beverly Hills to Hollywood area and you don't have a lot of different stops to make, you might consider skipping the rental car and expensive parking in favor of an airport shuttle (or FlyAway Bus to Downtown) to your hotel and taxis around the neighborhood. If you need to cross town a lot, it can actually be more economical to hire a car and driver than to pay multiple cross-town cab fares.
Public TransportationIf all your in-town travel will be between Hollywood and Downtown LA, then Metro service is actually reasonably efficient (except for after clubbing, since trains don't run that late). If you want to get back and forth from greater distances, it's totally possible, but takes a long time and can be quite complicated.
For a general overview of public transportation options, take a look at my LA Public Transportation Guide.
Also check out my tips on Riding the Los Angeles Metro to find out about some of its more peculiar aspects.