While it may look like you are just sitting there in staff pose, there is actually quite a bit going on. Proper alignment in Dandasana helps to inform alignment for other seated postures. It is to seated poses what Tadasana is to standing poses.
Sit on the floor with the legs extended out in front of you. Let the palms rest lightly on the floor beside you. In order to sit up straight, you need at least 90 flexion at the hips, so if you find yourself leaning back, you can sit on some height (a blanket or bolster). You might move the flesh out form under the sitbones here to help provide a more stable base. Keep your feet flexed and draw the outer edges of the feet back so that they are flush with the inner edges. This will help to rotate the thighs toward each other. Draw the inner thighs back toward the sitbones and at the same time, press through the heels. The thighs should be engaged here so the kneecaps are pulled toward the hips.
As you ground through the sitbones, lengthen the front of the body (without puffing the chest out) and draw energy from the base of the tailbone up the spine as you lift the crown of the head up toward the ceiling. Draw the shoulderblades down the back without hardening the lats, and make sure the shoulders aren’t rounding forward. Gaze straight ahead with the chin parallel to the floor.
Normally, Dandasana is used simply to set alignment in between various seated postures, but it can also be valuable on its own, especially for beginners. You can check out your alignment (and work to develop strength in the pose) by sitting with your back to a wall. Try and let the sacrum and the shoulders touch the wall, but no other part of the back. As you develop strength and flexibility, try and rely on the wall less and less until you can feel comfortable coming away from the wall entirely.
If you have any questions, please leave a comment below. I’d love to hear from you or see you at one of my classes!