Yeah I was going to mention the Gray Line link as well (The one hlbtimes2 posted)
I have taken the Gray Line bus every single time I have gone to Hollywood and its been FANTASTIC!!! Note that the prices on Gray Line for tickets are bit more expensive then anywhere else by about $15 but thats because of you paying for transportation there. But it is well worth it.
The bus picks you up from your hotel (or the closest bus stop to your hotel) and then will take you to Universal, then pick you up from Universal and will take you right back to your hotel.
For us its less hassle then renting a car and is super convenient. Besides that the bus drivers are very knowledgeable about the areas in Anaheim all the way to LA and will tell you where different movies and TV shows were shot. A few of them being Speed, Terminator, Gilligans island, and they will also point out locations such as the Hollywood sign, the Lakers Sadium, Capitol records etc. They give you a whole sightseeing tour on the way down for free basically. These are things you will miss if you are driving, or would drive right passes and not think about them having used that location your driving on for a movie. ALSO on the way home they usually pop in a movie for you to sit back and relax to while the bus drives you right back to your hotel.
Gray Line also has a Deluxe combo for Universal and a sight seeing tour. This is what I am doing in June. We get picked up at the hotel, go to Universal for the whole day, get picked up by the bus at Universal, which then takes us all around LA for more sight seeing at the Hollywood walk of fame, the Disney concert hall etc. before bringing us back to the hotel.