Background: have only meditated about 40 hours in my life, made a resolution to sit 2 hours a day in 2013 and shortly after read MCTB

I don't understand, in practice, how to focus on concentration and developing samatha jhanas vs. just ending up doing a vipassana sit..
From what I can tell the main difference is that for samatha you focus on continuity of the breath whereas for vipassana you notice sensations as they arise, which feel discontinuous. But in practice I don't understand how to focus on continuity of the breath. I am better able to focus on continuity when I don't limit the area of concentration, and feel the breath flowing in the nostrils then down through the body to the belly. But if I just focus on the nostrils snd nowhere else, the breath becomes discontinuous, a lot of the time I feel nothing and otherwise I feel mixed sensations of the breath that are not continuous in any way. If I continue focusing only at the nostrils, I feel like I'm doing vipassana instead do to this feeling of discontinuity.

Also, is there a difference between what to do with thoughts between samatha and vipassana? In both cases I'm mindful of the thought for a short moment and then direct my attention back to the breath.

My experience has been that the two should be developed together. The spiritual faculty of concentration is used to make the mind tranquil so that you can then clearly see (vipassana) arise and pass away, which is the development of the wisdom faculty. As this process continues, wisdom allows deeper and more subtle aspects of the mind to be seen, although this requires further stilling of the mind / increased tranquility.

Also I suggest investing time exploring the breath without any expectations. See how it flows down to the belly. Especially notice how trying to maintain awareness of the breath can at times make it feel rocky because you feel as though you are unintendedly trying to control it - who is "breathing?" I mean this in the sense that any time it feels like you or some agent is pulling air down into your lungs or expelling it from the lungs, notice the sensations of feeling as though there is someone or an agent "controlling" those muscles.

Sometimes people get frustrated that they aren't somehow watching the breath the right way. A useful trick is to question why you aren't already meditating perfectly (by whatever standards of watching the breath you have). Then notice all the phenomenon that seem to block you from meditating perfectly and where / how those phenomenon seem to come from and notice how they disappear.

Hopefully you find some of this helpful!

Hey super fox, thanks for your post.

I just did a one hour sit where I ignored the traditional advice of focusing at the nostrils, and instead followed the breath through the body, paying a lot of attention at the belly. Although I still got distracted by thoughts/sounds, I felt like I had a more tangible object to latch onto. By the end of the sit I felt more concentrated than usual, and it was the first sit where I wasn't eager to get up after my timer rang. I'm considering ignoring the advice of concentrating at the nostrils and instead focusing on the breath as it flows through the body - good/bad idea?

I think it's a good idea.

Personally I think it's useful to at times take the attitude of a scientist in a laboratory - that means patience and curiosity with acceptance that you're going to go down a lot of weird paths that might not always be fruitful. Form hypothesis/strategies as to what might be interesting and try them out. It might seem frustrating at times, but I think it's something you simply have to get use to. Also your practice will evolve over time, and learning how to adapt is an important skill.

I also think it's a good sign that you weren't eager to get up after your timer rang. Keep going at it and see if you can start to enjoy the process or transform it into a game or develop a sort of healthy-competetive attitude that allows you to build a skill like weight lifting, solving integrals, etc.

Also don't feel that you're "latching onto" an object - you don't want to cling to the object, you want to simply maintain it in your awareness. Think of the breath as your anchor point - the breath is a process that consistently appears in your field of awareness and serves as a reference point to return to when you get distracted. Eventually as the mind settles down you will be able to effortlessly follow the breath while magically being aware of the entire field of experience.

Search for empty0grace on youtube, many of his video-lectures were extremely useful to me on a practical level at the beginning of my practice (in the past he has posted a few times on DhO actually). Especially keep an eye out for mindfulness and the role it plays in your awareness and how to develop it.

http://www.dharmaoverground.org/web/guest/discussion/-/message_boards/message/3631675