What is posture?
I don't want to talk about some sort of prescriptive posture, the one in which your mother prodded you in the back and told you to stand up straight. I know I hated being told how I 'should' be standing so I won't be telling you how you 'should' be standing either. I want to talk about the attitude of becoming aware of your posture and enquiring into it. Taking the approach of looking at how your posture is and understanding how it is the way it is, is a great step to helping you move with ease.
I would say that posture is how you stand with ease. How you stand without putting undue pressure on any part of your body. Due to injury and stressors in our lives we become unaware of how our bodies become out of balance. The process of enquiring into how we are standing and moving helps us to become aware of our bodies' again and allows us to get back into balance so that we can dance with more mobility and freedom. I would say that posture is about more than standing up straight and more about being in alignment and moving with ease.
Becoming aware of your posture
Any body practice is great for becoming aware of how you hold your body. Maybe it's a yoga practice, Feldenkrais, somatic movement or even a moving meditation – there are tons of ways of enquiring into your own body, more and more each day are coming to life. But at the end of the day, it's about becoming aware of how you do things, not about the end goal of having done something. Years ago when I was doing loads of fitness classes, I used to crank my body to the edge of it's capacity, and I loved it at the time because I that's what I loved to do. But I couldn't hear if I was hurting myself because I was so focussed on the end goal of having done so many reps or minutes, etc. that I didn't look much at how I was doing my movements. Now I've started enquiring into how I can move in alignment and take note of how I'm moving, it's really helped my body move more easily.
The bottom line.
I advocate taking time to make a practice of noticing your posture. You don't have to change it, just notice it. The changes will come of their own accord, what you want to do is just notice how you are, then you will move towards how you want to be.