Usually start near Ralph B Clark Park taking the Castlewood trail to Nora Kuttner. There and back is roughly 4.5 miles. Some mild hills, nothing too strenuous. Makes for a good run. Parking is much better by Clark park on Rosecrans ave. Access Castlewood trail just east of the firehouse. Eazy Peazy.
Kalisev i. on Nora Kuttner Recreational Trail
Nice, short equestrian/hiking trail that also splits into a mountain bike trail. Very busy on the weekends. Pretty empty on weekday mornings. Coming from Euclid and heading west, it's uphill most of the way. There's not a lot of convenient parking at this end, though (so if you wanted to double-back and end with a nice downhill, you need to head into the neighborhood on the other side of Euclid and cross-over). Otherwise, parking is way easier on the east end, but be prepared to work harder on your way back to your car. There are several access points along Camino del Sol, or you can try your luck parking at the trail head at Castlewood/Parks. It's a little bit of a bumpy trail, but not very gravelly. Occasional piles of horse manure to avoid., but nothing egregious.
This is a short point to point trail that runs from near Gilbert St. to Euclid Ave. in Fullerton, along the outskirts of a residential development. Part of the trail runs through the Robert Ward nature preserve. The trail can be done as a part of the much longer Fullerton loop.