What to Pack
This is what I was most concerned about! Since we were traveling Seoul & Shanghai (~50°-60° most days) in addition to the Olympics, we needed to pack for those parts of the trip as well. The Olympics were between 20°-30° which made it easy to pack for because you essentially wear the same thing every day. We bought a bunch of hand warmers + toe warmers in the states and stocked up on Korean body heaters/hot packs (the same thing, but larger and come with an adhesive back). Most days I wore on bottom: under armour base layer, leggings, jeans; on top: under armour thermal, long sleeve shirt, sweatshirt, packable down jacket. Also, 1 or 2 pairs of socks, lined snowboots, a neck warmer, hat & mittens. Since no one can see your layers, we rewore things a lot, and my sister & I swapped some items to change things up. The indoor venues were a comfortable temperature, but the outdoor venues at the mountain cluster were very cold! They only way to prepare is wear a lot of layers. Through writing this post, I just found this helpful packing guide as another reference.
One thing I google searched a ton was restrictions the International Olympic Committee had on bag sizes and cameras. I wanted to bring my canon 6d DSLR + 35mm f/1.4 lens, and was fearful they wouldn't allow it. The only information I found was that your setup couldn't be longer than 300mm (11.8in) in length so I was good to go. I saw many DSLRs with crazy long telephoto lenses so I think most spectator's camera setups should be fine. I believe the bag size was restricted to 50cm x 50cm x 50cm because that's the size of the scanner. We brought a small backpack and had no issues going through security.