Sun Valley is considered “America’s First Destination Ski Resort” -- so you better spend some times on the slopes while you’re there. You can peep the world’s first ever chairlift on Ruud Mountain (sadly defunct now but still an impressive piece of history). If you’re a beginner, Dollar Mountain is the place to get your start, because it’s practically treeless. (So even if you’re clumsy, you’ll rock it after a few lessons.) For more advanced skiers, Bald Mountain is an Olympic training site -- so if you’re trying to humblebrag to your friends, this is the route to take...assuming you have the skills to tackle it.
Even supremely advanced daredevils will find a challenge at the Sawtooth Mountains, which comprise one of the best spots on earth for backcountry skiing. If you have to look up what it is, you're not ready to do it. In fact, even if you know what it is, you're still probably not ready to do it. Experts only, please.