It depends what you like to do or what you have in mind. LA is filled with tons of things to do, but it is so spread out.
Traffic is going at all times of the day so if you plan something to do, try and do something else after that near by it since you'll have to be stuck in traffic going home. In other words, be efficient.
- Petersen Automotive Museum is a good recommendation.
- The beaches would be something that almost always come up, Venice (not as many tourists, but still has plenty) or Santa Monica Pier (very crowded- if you want to be around tourists then this is your spot lol). The more south you go, the less crowded in terms of tourists (i.e. Manhattan Beach is excellent)
- La Brea Tar Pits
- OUE Skyspace LA Observation Deck *new attraction in the last year or two* (observation deck near the top of the US Bank tower- 3rd tallest building west of the Mississippi River)
*I was just there Tuesday and took some pictures, it was incredible, I'll see if I can post one to give you an idea.
- Griffith Observatory
- The Getty
- Hollywood Sign Hike
- Walk Of Stars
- Rodeo Drive if you like shopping and things of that nature
- Beverly Hills (drive around and see some of the historic mansions)
- Malibu (the view once you get there is beautiful and the drive can be scenic with windy roads)
- Tons of restaurants if you're a foody
There are tons of other things, but it's a quick list. If you have specific questions or certain things you're looking to do then shoot me a PM.
EDIT: Heres a picture from the Skyspace Deck
