Ah, the classic Los Angeles freeway skyline! Beautiful, isn't it.
Step 1: Rent a room at the Hotel Angeleno, as near the top floor as you can.
Step 2: Wait until it gets dark, but hurry before traffic dies down. (Kidding! It's L.A.!)
Step 3: Six second exposure at f/11 at the camera's base ISO, on a tripod of course.
Step 4: Done! Go have a drink by the pool before hopping on the bus to see David Gilmour at the Hollywood Bowl. Yes, that's right, photography is a process.