Establishing What is Not Dhamma

I realized that often, individuals provide insight which differs from typical Buddhist philosophy. For example, people either allude to a self in some way, or deny the dissatisfactory nature of phenomena. They might, in this last case, advise spiritual achievements leading to joy, but not equanimity and detachment. My question is : **what is the best way to recognize such non-Buddhist teachings?** I mean this especially in regards to (1) obviously non-Buddhist teachings (e.g. a person putting forwards an existing self) and (2) seemingly Buddhist teachings (e.g. deviating views on emptiness, compassion). So: **What is the best way to recognize authentic Buddhism?** I think this question is complex, and study and contemplation might be involved, but I am curious as to your answers. Thank you.