The More or Less Iron Laws of the Stretch Series (Gathered from Coach’s comments within each stretch series video and from other coaches/experts on the forum). Please add anything I've overlooked. Thought this might be helpful at the start of the new year, with a likely flood of new subscribers to GB.
1. Do a stretch series (approx 45 minutes) once per week. No, don’t do the whole front split series 2 or 3 times per week -- you’ll be so sore that you won’t make much progress --same goes for thoracic bridge and middle split.
2. You CAN work on stretches that you are not very good at outside of that once-per-week stretch series, but keep the intensity LOW (3 or 4 out of 10 on the intensity scale)
3. If a stretch is PAINFUL and/or you think you are injured, stop -- you are either injured or doing the stretch incorrectly.
4. “Mildly uncomfortable” is what you want, NOT “agony”.
5. If you stretch with the same intensity with which you do conditioning work, you will likely get injured.
6. It takes 9 months or longer to make substantial changes to your flexibility/mobility. Take the long view and keep the intensity of your stretches low.
7. APT = anterior pelvic tilt (a slight arch in the back); PPT = posterior pelvic tilt
8. If you are not sure if you are doing a stretch correctly, take a video of yourself, put it on YouTube as an unlisted video, and then submit that video in the video review section of this website. An expert will give you excellent feedback.
9. You might not be able, at first, to do the more advanced stretches late in each series. That’s OK. As your flexibility improves over time, try adding those more advanced stretches. (Or, as Jin suggests below, scale/modify those stretches)
10. Do the stretch series at the end of your workout
11. Have fun and enjoy the process (courtesy of Etienne)
But always make sure it's safe and not counter-productive (get coach's approval is the way to go)