in my opinion, according to the Anapanasati-Sutta one shouldn't follow the breath inside and outside the body. One should set mindfulness to the fore. Do not follow the breath with mindfulness, set mindfulness on one point and just breath mindful, meaning "know" the breath but don't follow. I don't know how to express myself better. I hope you're able to understand exactly what I'm trying to say.
MN118 Anapanasati - Sutta wrote:There is the case where a monk, having gone to the wilderness, to the shade of a tree, or to an empty building, sits down folding his legs crosswise, holding his body erect, and setting mindfulness to the fore. Always mindful, he breathes in; mindful he breathes out.
The point itself where mindfulness is set isn't the most important thing. Like Ben already said, some prefer the area around the nostril, some the rise-and-fall of sensations either at the point of contact of breath and skin, or some other place such as the abdomen. All these places are interrelated with the breath, thus one is, when mindfulness is set, able to breath in, always mindful and breath out, mindful.
just my two cents,
best wishes, acinteyyo