I didn't follow any system, just tried stretching exercises I remember from my days of doing karate as a kid and another exercises I was taught on physiotherapy.
You know basic stuff, trying to touch my toes while standing. Some hand stretching. I guess it was totally ineffective, but number of nights with migraines are down a lot.
Careful with the toe touch, can aggravate certain back issues. Try diagnose with what you suffer and target the weaknesses.
Generally cobra stretch type manoeuvres are a good starting point. Don't neglect some strengthening of the upper/mid back, even if it's just some resistance bands etc.
