These hikes are best summed up in the Boy Scout motto: Be Prepared.
If you're ready for 20 percent grades up several miles of trail, you'll discover some of the most awesome vistas in the San Francisco Bay Area. The hills of the Diablo Range stretch to the horizon from many East Bay ridgetops. A dusting of snow from passing winter storms makes them look positively alpine.
Best time to go: March through May, when the hills are shimmering green and the wildflowers are out in full bloom. Winter's the next-best time, provided you give the trails a few days to dry after the winter storms blow through (though hardy hikers can't resist the urge to hike to the heights the few times a year when the peaks are snow-capped).
About the only time to avoid the East Bay hills is in the depth of summer, when blazing summer heat makes the trekking miserable.
These hikes are within the ability of intermediate to experienced hikers. Rookies hoping to push their boundaries should make sure they have the right gear, plus water and snacks to sustain their energy level. Also: Be ready to turn back if it's too much.
Flag Hill Loop at Sunol Regional Wilderness is the least strenuous of the bunch, yet it requires 900 feet of ascent over 1.3 miles. The loop at Briones Regional Park is moderate by East Bay standards -- more miles than Sunol but fewer steep climbs.
Mission Peak, Mount Diablo and Murietta Falls are significantly strenuous outings that in many ways are the most rewarding.
What to bring:
Clothing in layers (expect strong winds on the high ridges).
Water and snacks
Trekking poles if you use them