I believe the update is awarding sites with fresh, original and constantly updated content. Also, I believe sites will be rewarded if they have a constant flow of user activity.
I know many of you might have static websites or sites that don't change very often. I'm thinking these 3 adjustments will help your sites climb back up if they have fallen, or just climb up in general for a new sites, etc.
1. Obviously keep the fresh content going and don't leave your site in the dust.
2. Have an active website with users commenting and subscribing to your feed.
3. The other 2 many of you probably knew, but I'm thinking related backlinks will have an impact from the caffeine update. The update is supposed to retrieve fresh and highly related content to what the user is searching for. So if you have a site on flowers for instance, it's best to gain backlinks from sites that involve anything about flowers...different kinds, types, colors, etc. If google sees that your sites has many links from highly related sites pointing to your site on flowers, I believe it will have a greater impact than before the caffeine update, in which a pr 5 is a pr 5 is a pr 5, doesn't matter.
So that is just my theory, very basic I know, but might help some people think about it.
Anyone have a different theory or even results about the new update?