Renting a car in LA is a must, because you can't expect the friend you're visiting to pick you up at the airport every time...
Some great ways to save money on your rental is to Google promo codes for the different rental companies or check out sites like Price Line, which allow you to set your own rental price.
If you're staying for over a month, some of the rental companies even offer month or more discounts.
When searching the internet for rental prices, make sure to search at different times and days. Most rental companies are like airlines, there is no rhyme or reason to their pricing.
In addition to the regular rental companies such as Budget, Enterprise, Advantage, Hertz, Thrifty and National, there is also Rent a Wreck. The prices are better, but their name is no joke. So if you're trying to impress the big producer you're meeting for lunch on Sunset, park around the corner.