Number one you need to dress in layers. Base layer top and bottom, thermal top and bottom, do not bring cotton hoodies bring fleece or wool. Bring a few pairs of socks but I'd only recommend one pair of underwear (the one you wear there), an extra fleece, and an extra pair of pants (if you're feeling adventurous) as far as clothes go. Obviously bring a parka, gloves, hat, etc. If you don't have a four season tent I'd bring a zero degree bag; if you have a four season, a 20 degree bag, and dont want to spend the money on a new colder rated bag I'm sure you'll be fine. Conversely, if you don't have a four season tent or a zero degreee bag you can pick up a fleece bag liner at any big store for like 15 bucks that you can put inside your bag. Remember your sleeping pad. These recommendations are based around marginal activity and sleep conditions. If you plan on backpacking into somewhere, double up on your thermals and socks since you'll be getting sweaty and sweaty=wet... not a good combo in winter so you'll need to change when you stop to set up camp. Also, bring some whiskey. No it doesn't make you warmer, but up here no one goes camping in the winter without a little booze to lighten things up. Even if you LOVE the winter camping outside in 20 degree weather has the tendency to make a person miserable under the right conditions. Also a few tips: When you go to bed, put your water bottle in the snow mouth first. The snow will insulate the water so you dont wake up with a bottle of ice, and what ice does form will form on the bottom of the bottle since its upside down thus not blocking you from drinking. If you're at a high elevation, do not underestimate how much water you'll need. Being up high in the cold dehydrates you pretty quick. Finally, since it seems like you may not have a bunch of experience, spring for some mountain house food. If you don't know exactly what you're in for, a good, great tasting, hotter than hell meal to look forward to always helps. If you're having a hard time and only have a packet of ramen to look forward to, as a newbie, it may only make things harder. GOOD LUCK! I hope you have fun. I haven't been able to go camping the past two weeks so I'm jealous.