Avoid it. When confronted with a section of loose or blocky rock, first look for ways to climb around it. Bad rock is often found in the nebulous, moderate terrain on multi-pitch routes, where thoughtful route-finding will get you past chossy sections in relative safety.
Inspect your holds. If you must tackle a chossy section, carefully inspect each hold before you touch it. Are there fracture lines around the hold or is it securely wedged? Test the hold by gently tapping on it with the palm of your hand. If it sounds hollow or vibrates, tread lightly. Remember, a chalked hold is not necessarily a solid hold!
Be delicate. Imagine how the vectors of the various forces you’re applying to the hold will affect it. Never pull directly out or towards yourself with a suspect hold — this could lever it right off the wall! Pull straight down instead, moving as fluidly as possible and keeping your weight over your feet.
Plan for the worst. Distribute your body weight so that if the hold breaks you can recover your balance in time to avoid a fall. If you yard the hold off, yell “Rock!” as loudly as you can. Plan for loose pitches by stationing your belay, and your belayer, out of the line of fire.
To pro or not to pro? Unfortunately, there’s no pat answer when it comes to protecting loose rock. The psychological security afforded by a piece (however crappy it may be) may not offset the danger of simul-falling with a jagged block that your pro has just levered out. Though cams often provide more security than passive pro, it’s often better to suck it up and skip the placement altogether.
Know the season. During the spring — with its significant freeze-thaw cycles — and after spells of heavy rain, the cliffs are at their most active. Hollow plates, loose blocks, and flexible flakes may be more unstable. Be extra “heads up” at these times.
Most important, there’s no need to tempt fate by not wearing a helmet. With the new ultra-light models on the market, you’ll almost forget you have it on your head.