You should try one of these 10 day Vipassana courses that they have all around the world (S.N. Goenka).

For the first 3 days or so you observe natural breath. As it comes in, as it goes out, sometimes through the left nostril, sometimes through the right, sometimes a short breath, sometimes a long breath.

I think it's called Satipattana and they use it to try and establish a constant mindfullness.