Gil Fronsdal leads an Anapanasati 4 Forms of Mindfulness of Breathing. There are different kinds of awareness and here are 4 different approaches.
How we can be aware is very variable.
As you breathe in more deeply in a simple gentle way. Feel the lifting and stretching of the rib cage, lifting of the shoulders. As you breathe out, experience whatever sense of release or relaxing. Settling back of the torso, the rib cage, and the shoulders.
As you exhale, see if you can let go of your thoughts, so you can better feel your breathing.
And letting your breathing return to normal, and with the normal breath, do the same thing, feeling the lifting of the rib cage, the torso, the shoulders, as you settle on the exhale.
There's a rhythm of expanding and contracting, lifting and falling, inhaling and exhaling. See if you can tune in to that rhythm. If it's fast or slow. Deep or shallow. Comfortable or uncomfortable.