Hermosa Beach is simple: the beach, the pier, the Strand, and the streets around Pier Avenue. The Hermosa Beach Pier is the obvious landmark, while the Strand is the best way to stitch together Manhattan Beach, Hermosa, and Redondo on foot or by bike.
For something more local, look for live music at the Lighthouse Cafe, or time a visit around beach volleyball events when the sand becomes the centre of town.