It’s the regular routine: several featured games a day at ridiculous prices, and if that’s not adequate, you can buy 10 Half-Life 2 or 8 Deus Exs for $20 or lower. It’s worth checking out the daily discounts, but remember to wait until the last day of the sale before buying that game on your mind (assuming it’s not on sale).
As for the giveaways, each day of the sale, 30 people will be selected to receive the top 5 games on their wishlist. This of course can be found on your Steam profile and seems to have received some revamping since the initial launch.
It might also be an interesting idea to check out the content stats as a result of the sale.