Remember to keep your breath continuous so the tension moves naturally out of you and to keep your eyes relaxed so the head remains where it should be, between your shoulders and as a natural line with the spine.
Let the exhale lead most of the forward opening movement so the relaxation will be greater and your rib cage will open as well.
Keep your feet relaxed and flat on the ground and use the knees and hips to navigate this way.
At the end do a few reverse movements where you lean from within the door frame back to feel if you moved more than you wanted to and to let the density built in the extra shoulders move in the body and return to where it should be.