Skiing and snowboarding carry real risk, and most of it is manageable. The code below is the standard set of expectations at every ski area in North America. It is not legal advice and it is not a substitute for the rules posted at whichever hill you are on, which take precedence.
The responsibility code
The principles are the same everywhere, and they come down to seven things.
Stay in control. Be able to stop, and to avoid other people and objects. Everything else follows from this one.
People ahead have the right of way. The skier downhill cannot see you. Avoiding them is entirely your responsibility, not theirs.
Do not stop where you obstruct a trail, or where you cannot be seen from above. Stopping just below a rise or a blind roll is how collisions happen. Move to the side, and stop somewhere with sight lines.
Look uphill and yield before starting downhill or merging. You are entering someone else's path.
Use devices to prevent runaway equipment. A loose ski travels a long way and hits people.
Observe signs and closures. A rope across a trail is there for a reason, and the reason is often not visible from the top of it.
Know how to use the lifts safely, and ask if you do not. Lift staff would far rather explain than deal with the alternative.
What this actually means in practice
The commonest cause of collisions is a faster skier overtaking too close. There is no defined passing distance; the working rule is to leave enough room that a sudden turn by the person ahead does not matter.
The second commonest is stopping in the wrong place — under a lip, at the exit of a lift, or in the middle of a narrow section.
The third is skiing beyond ability, which is generally a decision made at the top of a run by someone who does not want to walk back down. Walking back down is always available and nobody cares.
Judging ability honestly is harder than it sounds, and the test is set out on ski and snowboard lessons.
Helmets
Helmets are not mandatory for adults at most areas and are worn by the large majority of skiers and riders. They are cheap to rent and included in many packages — see rentals.
For children they should be treated as compulsory regardless of what the rules say.
A helmet protects against a specific class of injury and does not make anyone safer at speed. It is not a licence to ski harder.
Terrain parks
Jumps and features carry a different risk profile from ordinary trails, and the rules are stricter for good reason.
Look at a feature before riding it, every time. Features change with grooming and weather, and a jump ridden yesterday is not the same jump today.
Do not stop in a landing zone, and do not drop in without checking that the previous rider has cleared.
Progress in order — small features before large ones. Most serious park injuries involve someone attempting something a size too big.
Hazards specific to these hills
Ice. New England produces thaw-freeze cycles that turn groomed snow into a hard, fast surface. This is the defining hazard of Berkshire skiing, and it makes edges and control matter far more than on soft snow.
Man-made snow is denser and firmer than natural snow. A fall on it is harder.
Snowmaking equipment. Guns and hoses operate on open trails, often at night and early morning. The area around a working gun has poor visibility and a lot of hardware on the ground.
Trees and trail edges. Small hills mean narrow trails and short runouts, and the boundary comes up quicker than at a large resort.
Night skiing. A lit trail has flatter light and less depth perception than the same trail at midday, and the temperature drops sharply after dark. Operating hours are on when the hills run.
Wind holds. High wind stops upper lifts and concentrates everybody on the lower mountain, which makes it considerably busier than usual.
If something goes wrong
Report an injury to ski patrol rather than moving an injured person. Cross a pair of skis in the snow uphill of them to warn other skiers.
Stay with the person. Send someone else to the nearest lift or patrol point.
If you are involved in a collision, stay. Leaving the scene of a collision that causes injury is a serious matter, legally and otherwise.
For beginners
Almost all of the above is easier if the first day is spent with an instructor rather than a well-meaning friend. What that involves is on learn to ski or snowboard, and the practical preparation on tips for a first day on the slopes.
Off the snow, the hazards worth knowing about are ticks in the warm months and thin ice on the ponds in winter — both covered on wildlife and on the water.