The breathing is often the last thing that comes together in our yoga practice but it is the most important.
The breath is what guides us to a place of deep meditation during our movement but it also supports our practice physically. I often say "power your body with your breath , think of the breath like the wind in your sails"
So during your practice you should inhale from your solar plexus area, expanding around the complete circumference of your lower ribs and exhale from your naval centre gentle pulling your belly button in towards your spine. ( place your hands on rib cage and then on belly until you get the hang of it) This is key as it keeps the yogic locks engaged so you have the strength and elevation needed for a strong, supported, smooth practice. But it also means you work your deep core muscles, all four layers of them and of course their connecting muscles that help create the beautiful moving phenomenon that we are :-)
We often get caught up in wanting an enviable washboard belly but we must be careful not to block our creative, sexual centre at the core, we want to be strong and toned but not held and ridgid. On a physical level strengthening our core is key for lower back support, stabilising the pelvis and allowing us to open our chest and give us more heart space. And on a subtle level we need freedom at the core be be expressive, sensual and move with tha natural ebb and flow of life.
When we use our bodies in a dynamic way, as we do during a flowing yoga class our whole body is engaged at every stage. Our bodies become a continuous web, every muscle working together, there should be no separation, no isolation, watch a cheetah run, a deer jump or a snake move through the grass and feel that in your body as you move. Find your feline agility, the spring in your step, don't miss an opportunity to use your body properly and you will see your body change shape, be sculpted, feel light and athletic.
I used to joke with my father that my body was my earthly vessel, but in earnest I did have a sense from an early age that this vessel was sacred and I needed to care for it. So remember to love, honour and be kind to your body. It's the only one you've got and my goodness it tries its hardest to be the best!
Although you need to be using your core throughout your practice here are some poses that will deepen your awareness and increase your core strength
1. Dandasana The Plank- plank as often as you can. Hold it for 10 breaths and build up, make sure your chaturunga is slow and controlled as you lower yourself towards the earth.
2. Bakasana The Crow. Don't be fooled by thinking you need arm strength. It's really a core asana
3. Sirsasana Headstand- by doing your headstand against the wall you miss the most import lesson, how to engage and have full control over the inversion with your core. You may be upside down but you aren't doing headstand! Use the wall as your emergency but try not to touch it. Then Pike and learn what those tummy muscles are really made of! 
