Length of trip, location, type of skis, and weather determine what cross-country skiers should bring with them.
Every cross-country skier should have a small pack to carry things in. This can be a fanny pack or waist pack for a few essentials, or a larger day pack.
Clothing is perhaps the most important gear skiers will bring with them, as clothing keeps them safe and comfortable. One longtime skier says, "There's no such thing as bad weather, just bad clothing." Think layers, and wear the right amount of clothing to stay warm without becoming overheated. It's OK to start a little cold, and warm up. Always have extra hat and spare gloves or mitts, in case of loss or getting wet. Bring a warm fleece, wind breaker, and wind pants, especially for longer trips in remoter spots.
Bring water and a snack or lunch depending on length of trip.
Bring a map of the trail system, or a topographic map of the region, and plan the route before setting out.
Carry a first aid kit appropriate to the outing. Have a few band-aids and moleskin at minimum; expand on these items for longer outings.
Waxable skis? Bring wax appropriate for the conditions, and a scraper.
Leaving late in the day in a remote location? Bring headlamp to light the way home.
Longer outing in more remote places? Bring a small repair kit that includes an emergency ski tip to clamp onto a broken ski, some duct tape, a few feet of wire, and an all-purpose tool such as a Leatherman knife.