@cicerone imposter,
We're talking about common issues, not common beliefs. Common issues such as how to survive and thrive in a believers world. That formz a solid common ground of day to day experience and challenges.
As for beliefs, common ones are easy to spot too, once you put your mind to it seriously rather than just dismissing the question off hand. Off the top of my head,most if not all atheists I know believe that God(s) or other magic forces do not intervene in this world and that all that happens in this world is therefore entirely natural and
not supernatural. Many if not all atheists consider religion dangerous for society in some way or another. They often support science and education as good ways to promote social progress. They tend to embrace the separation of church and state, etc. These are all rather trivial.