SharePoint 2013 includes Like and Rating functionality out of the box. Just navigate to List/Library Settings -> Rating settings and set it up. It is that easy .
However, you can only like/unlike or rate a item/page in the “All Items” view of the list/library. So, If you want to show this flashy “Like” functionality to your users on different publishing pages of your site, there is no out of the box way to do it.