The way of practice suitable for realizing Nibbāna is to see the six sense bases and their objects as not-self.
Anattanibbānasappāya sutta - Not-self As Suitable For Realizing Nibbāna
"I will teach you the way of practice that is suitable for realizing Nibbāna, bhikkhus. Listen closely.
And what, bhikkhus, is the way of practice that is suitable for realizing Nibbāna?
Here, bhikkhus, a bhikkhu sees the eye as not-self, sees forms as not-self, sees the arising eye-consciousness as not-self, sees the arising eye-contact as not-self. Whatever feeling arises with eye-contact as its condition — whether pleasant, painful, or neither-painful-nor-pleasant, he sees that too as not-self.
He sees the ear as not-self, sounds as not-self, sees the arising ear-consciousness as not-self, sees the arising ear-contact as not-self. Whatever feeling arises with ear-contact as its condition — whether pleasant, painful, or neither-painful-nor-pleasant, he sees that too as not-self.
He sees the nose as not-self, smells as not-self, sees the arising nose-consciousness as not-self, sees the arising nose-contact as not-self. Whatever feeling arises with nose-contact as its condition — whether pleasant, painful, or neither-painful-nor-pleasant, he sees that too as not-self.
He sees the tongue as not-self, tastes as not-self, sees the arising tongue-consciousness as not-self, sees the arising nose-contact as not-self. Whatever feeling arises with tongue-contact as its condition - whether pleasant, painful, or neither-painful-nor-pleasant, he sees that too as not-self.
He sees the body as not-self, tactile sensations as not-self, sees the arising body-consciousness as not-self, sees the arising body-contact as not-self. Whatever feeling arises with body-contact as its condition — whether pleasant, painful, or neither-painful-nor-pleasant, he sees that too as not-self.
He sees the mind as not-self, mental phenomena as not-self, sees the arising mind-consciousness as not-self, sees the arising mind-contact as not-self. Whatever feeling arises with mind-contact as its condition — whether pleasant, painful, or neither-painful-nor-pleasant, he sees that too as not-self.
This, bhikkhus, is the way of practice suitable for realizing Nibbāna."