This tutorial shows you some modifications for tightness as you forward fold.
This is a way to modify your sun salutations as you increase your strength.
This is a tutorial showing how to move from plank to upward dog. Chatturanga is a very difficult pose requiring a lot of abdominal and upper body strength. Holding plank is a way to increase that strength without putting the shoulders at risk. Proper alignment of upward dog is showed here as well.
This is an explanation of how to step back to plank and then to lower to chatturanga. Rememeber to keep the gaze slightly forward while moving through chatturanga, instead of letting the head drop.