In the attached video you will find a step-by-step instructions for the Headstand (Shirshasana, Sirsasana) Yoga asana. The video itself is generously commented with all the details about benefits of the yoga pose, it has variations from the basic pose, to twists to the Scorpion Yoga asana. Many other details are discussed too:
correct head position
half posture as the base for the full asana
correct arms (elbows) position to have good base for balancing
exercise to strengthen arms, shoulders and chest to get some pressure from the neck out
leg raises to strengthen abdomen and lower back
etc.
If Sirsasana looks to hard for you, practicing Shoulderstand Yoga pose (Sarvangasana) is a good substitute: link to the article with two detailed videos on Sarvangasana.
neck overstretch in the asana and it's prevention, massage of the hear muscles with more blood going down when body is in inverted Yoga pose, Shoulderstand as a substitute for the Sirsasana (Shirshasana), etc.
