On certain projects, I start with a very specific detail. In this case, I started designing the headlights before I started designing the body. For this project I wanted the main focus to be on the headlights from the front view, so I did many quick sketches as I worked through some ideas.
One thing to remember: When making your headlights a main feature of your design, make sure that this design language is repeated in the tail light shape as well. In vehicle design, you want both design features to be related so it doesn't look like two different cars from different angles-- it should all relate.