A great source for Yoga Postures by Mark Giubarelli.
Lunge Pose Part of a Sun Salutation
Both hands are placed down supporting the posture.
On the back leg the ball points of the toes are touching down.
It may be easier to lean on the ball points of the fingers and have the palm off the mat. This gives a little extra raise and not so much compression around the abdominals.
Make the effort to look forward it stretches and opens neck muscles and abdominals. Most of the time people get lazy and Keep the head dropped.
When used in a step back or forward delay the breath whether you are inhaling or exhaling. The lungs are filled so much more from moving and breathing a slight bit in the beginning of the motion if at all rather than all of a sudden. You see is you bring the element of air in too quick it hits the diaphragm too soon and the breath stops.
Good transitional pose. Stretches the Psoas muscles and liacus, they run alone the inside of the groin and up through the inner pelvis.
If your neck is injured keep it straight rather than looking forward. Or just raise it a little so that your muscles stay strong. Notice the palms are flat on the mat. In the picture below from one of our Sun Salutation clips the ball points of the hands touch. This provides a little extra lift and reduces compression in the belly chakra.
Vinyasa Yoga postures to transition from and to:
From Tadasana step the legs apart. Turn one leg out and bend the knee over the ankle. From Uttanasana step one leg back and externally rotate it until the heel touches the mat. From the Downward Dog Pose step one leg forward between the hands. Externally rotate the back leg until the heel touches the mat.
Yoga Teacher Tips
It can be hard on the back if injury is present and this yoga position is entered too fast or too deep. It can also be a vary therapeutic yoga position when done mildly.