Google has always had Webmaster Guidelines. These can easily be found here. Some of the newer items include rich snippets, Responsive Designs for mobile friendly, and a tilt towards security, such as SSL enabled websites. The point being that Google is requesting more and more from webmasters, to the point of going past most novice web designers and developers.
All this means is that for SEO experts in 2015 it will require far more technical knowledge than before.
Location of course means more than it did ever in Google’s history. If you own a big pizza chain, don’t be surprised if the local mom and pop pizza shop beats you in the rankings when the search is made within X number of miles of their location, with the advent of mobile GPS enabled devices doing what most likely will be the majority of search traffic in 2015 to 2017.
Also more historical search traffic from your account will play more and more into the SERPS. Meaning if you searched for Pizza and clicked on mom and pop pizza, and didn’t hit the back button most likely they will continue to do so for you. In the whole if more people do that it will eventually start ranking for many people. It now appears to count almost as much as a backlink.
This means that Google’s search results are becoming more and more like a social bookmark rather than a search engine results page, or at least that is how many SEO’s are complaining about the results.
Other issues that we are seeing further growing of the news and local results displayed on the SERPS page. Meaning that before we used to be able to count on 10 results, now it could be as little as 5 or 6.
That puts a wrinkle on you going to your client saying “we’re #6” that used to mean page 1, but now it means page 2.
2015 is going to be an interesting year.