Here’s a lovely and precise instruction on how to practice breath awareness by Ajahn Chah:
Just be aware at the breath. You don’t have to be aware of anything else. Keep making your awareness more and more refined until it feels very small but extremely awake.
Keep watching the breath get more and more refined until there’s no more breath. There’s just awareness, wide awake.
Let go of everything, leaving just this singular awareness.
Don’t worry about the future; don’t worry about the past.
Stay right here.
– Ajahn Chah