The gate to Eaton Canyon opens around 7:30 so arrive early to avoid crowds and to snag closer parking. If arriving late, park in the huge overflow lot. Trail maps available on-line or in the nature center. The center doesn't open until 9am, but porta potties are located near trailhead.
Everyone's destination seems to be the falls, but if steps matter, head to Henninger Flats with an elevation gain of approx 1600 feet! The path is on a dirt fire road and on a clear day you can see downtown Pasadena and LA! Once at the top, stop inside the visitor center and check out the diorama and artifacts. Before heading back, be sure to take a peek inside the old fire lookout tower. For more info on Henninger Flats, see write-up under Angeles National Forest.
In summary, logged about 21k steps and 8+ miles r/t on exposed road. Tips: best during the cooler months; bring sufficient water; enjoy the other option!