Listening to one of Ayya Khema's many excellent recordings, I was reminded that there is not one but at least six different ways of being with the breath during awareness of breath sitting practice. Here they are:
In your head, count one on the in-breath, one of the out-breath, and repeat until you get to ten. Then start over . . . Any time a distracting thought interrupts, or you loose track, just go back to one.
If you don't like numbers, use one word, the same one on each in-breath and each out-breath. You can use the word 'peace' for instance, or any other that works for you.
If you have visual mind, imagine the breath coming in and out as an ocean wave or a cloud. When coming in with the breath, the wave gets smaller. As it goes out, it gets bigger.
Pay attention to the sensation of the wind of breath on the nostrils, or the throat, or the lung. Follow the breath in, follow the breath out. Make sure to continue to stay with sensations in the body.
If practiced already, you can notice beginning, middle, and end of each breath.
If you cannot work with the breath, look at the impermanence of each breath, the constant coming and going.
My practice of choice is the sensation approach, focusing on the physical experiencing of breath making its way through and out of the body. I have found focusing on the larger sensations such as the rising and falling of the belly much easier to do than let's say honing on the sensations in the nostrils.
Find the one that works best for you, and stick to it!