Eat and hang somewhere.
I like Santa Monica in LA cuz you can walk 3rd st, the pier and hang out on the beach. There other nice outdoor malls in the LA area that I like, the Grove is pretty nice, pleasant, classy outdoor common area and nearby farmer's market you can try some snacks while browsing around.
Also consider botanical gardens, nice atmosphere. Art festivals and museums are kind of nice also.
Try a bonfire by the beach sometime. Bring food, blankets and wood of course.
Italian restaurants in general tend to have good atmospheres, though I don't particularly care for italian food. Restaurants overlooking bodies of water are always nice.
I don't like movies for first dates cuz you don't get to talk to the girl.
One of these days, I will take one of my dates to the shooting range and/or illegal street races. :Q