This is the current advanced neck stretching protocol I use in the office. I find it especially helpful for patients that I see who have neck pain when they wake up in the morning, have tried regular static stretching with no improvement and feel like it's not one particular muscle but several on the side of the neck.
Here is the advanced neck stretching written out step by step for you:
1) move your neck in a big circular motion to identify the tightest ranges.
2) from that position, using your opposite hand, push your head into your hand contracting the tight muscles.
-I like to do 3 sets, 50%, 75%, and max % with whatever is comfortable
3) Press for 10 seconds
4) Keeping your head in the same tilted position, now place your hand on the opposite side and contract the muscles on the shortened side of the neck (if you're leaning your neck to the left, press left)
5) Following 10 seconds on each side. Move your neck in big circles, (I like 10 reps in each direction) avoiding any painful ranges of motion.
What makes this "advanced" is it's not an ordinary static stretch. Whenever possible active stretching like the version shown in this video is what I prefer in my office... FWIW!
Hopefully this advanced neck stretching helps out and if you have any questions be sure to leave them in the comments so I can get back to you!
When going over this neck stretching be sure not to go through any pain!
Reminder: I go over this advanced neck stretching with people in my office after I have done a physical exam and gone over their health history to rule out any contraindications!