Here are the most important things for any ski trip.
A Pair of Skis:
A good pair of skis will have sharp edges freshly filed, as well as having had the bottoms of the skis freshly waxed. The wax is to help cut down friction between the skis and the snow. This will allow you to o faster. Filing the edges makes them sharp so that if you hit a patch of ice while turning you will not fall or risk injury. You should also have the bindings adjusted for any weight changes during the year. Ski bindings are designed to release incase of a fall, but if the yare adjusted for a lighter person they could come off at the wrong time, and if they are adjusted for a heavy person you could hurt yourself.
Boots:
Even if your feet have stopped growing you still need to check your boots ever year, and every few years you should replace the foam inserts I your boots to make sure your boots are comfortable and fit properly. Improperly fitting boots can cause a broken ankle or at least some nasty blisters that could ruin your skit trip and hurt for days.
Your polls:
The ski polls you need depend on the type of skiing that you are going to be doing. Straight polls are for downhill recreational skiing and bent polls are for racing so that they can be tucked in behind your body to make your body more aerodynamic. Just like the edges of the skis need to be sharp the tip of the ski polls need to be regularly sharpened for the same reasons. Ski polls also provide balance for beginner level skiers. Ski polls have to be the right height for their user. When the poll is planted in the snow you want your hand to be on the grips and your arm should be bent at 90 degree angle.
Hand Protection:
Just keeping your hands in your pockets when you are on the lift is not enough to keep your hands warm. When you are skiing it is a must to have a good pair of gloves. The gloves must be insulated to keep your hands warm and be water resistant, to keep your hands dry.
Insulated Underwear:
Keeping your body warm and as dry as possible is very important if you are going to spend the day outside in the cold and wind of the winter and expect not to get sick.
Outerwear:
Outerwear for skiing has not changed much in the last 20 years, but the technology behind it has. Today's materials are thinner, less expensive and far more efficient at keeping the body warm and dry, while still looking good as well.