Skiing opens around Thanksgiving and on good years they make snow through June 1st, keeping only one long, wide run, "Superstar Glacier", open.
The skiing ranges from the very beginner slopes—great for learning, to tough mogul runs, and newly cut "natural terrain parks" through the trees that will keep advanced skiers busy, especially when there's plenty of snow.
For bump skiers, Bear Mountain (one of Killington's 6 areas) offers a classic bump run right under the lift that ends at a bar with music blaring, and people taking a break on the porch while watching the skiers coming down all day.
Killington has the most terrain, and the most snow making of anywhere in the East, meaning there are plenty of long cruisers for anyone looking to work on their turns.
Day passes run a pricey $70, but if you book online and in advance, you can save as much as 15%. If you're planning on going for more than a couple of weekends, buy your season pass before October: it costs around $400 with only a few blackout dates. This can be a steal if you're a regular weekend-er or can get up there for a week or two in addition to your weekend trips. This is an "All-East" pass that includes a number of other mountains, including: Mount Snow, Sunday River, Sugarloaf, Attitash and Pico. Normal All-East passes, bought in season without blackout dates, go for around $1000. All passes include lodging discounts, which can also be helpful if you don't have a place to stay.