While performing asana, there is so much more than getting your body into a position or pose. The process can be overwhelming; engage your core, notice the quality of your breath, notice your thoughts, notice any tension or compression in your body, etc. However, before you even begin considering these aspects, it’s important to be safe and not to cause harm, this is where the principles of alignment come in.
1. Foundation / Stability
When moving into a pose, ensure that you have a solid foundation.
Using Tree Pose (Vrksasana) as an example, starting in Mountain (Tadasana) pose and ensure that you are stable. To increase your stability, you can focus on (what is typical) the 3 points of contact your foot has with the earth; the heel of your foot, the ball of your foot, and the outside ball - this makes a triangle. Additionally, to gain more stability, focus on a drishti which merely is a specific focal point (a spot on the wall, on the floor, etc.)
Now that you have a solid foundation, you can begin to focus on the balance portion of the pose.
Continuing to move into Vrksasana from Tadasana, you can keep your hands at your side (or anywhere at this point) and begin to shift your weight into your left foot. Bend at the right knee and bring your right foot to your left ankle. You can modify this by bringing the sole of your right foot to your left calf or left inner thigh, ensuring that you do not place your right foot on the knee joint.
Focus on your balance and ensure you are grounded and stable before proceeding.
Now that you have a solid foundation and feel balanced, you can bring the spine into play. There are multiple movements of the spine that you can perform.
In the case of Vrksasana you can focus on lengthening through the spine.
The final principle of alignment is your extremities. After you have achieved the prior 3 principles, you can begin to your move arms/legs/hands/feet to modify the pose further.
While in Vrksasana, you can move your hands into prayer pose, keep your hands to your side, cactus arms, or any variation that you find helpful in your practice.
When you are first starting yoga or a new asana, you can focus on each one of these principles. Once you begin to obtain mastery of the pose, you can begin to incorporate noticing the quality of your breath, ensuring you are engaging your core, relax all of the muscles that you are not using (e.g., especially those in the face and tongue).
A practice that I enjoy doing is to spend 5-15 minutes working on a specific pose. I work through these principles, I may hold the pose (static), or flow (dynamic) in the pose matched to the inhale/exhale of my breath.