WOW! That is a lot of great advice you have been given thus far. I just want to offer a couple more pieces to help.
No matter the technique you chose to gain flexibility, proper alignment is a MUST. Just because something looks like a great stretch doesn’t mean it is, if parts aren’t in there correct places. With that being said, remember that stretching is really all about increasing the distance of the origin from the insertion of the muscle.
My second piece is about a having a system. When we talk flexibility, there are many ways to improve one’s range of motion. What I think is most important when dealing with clients is have a system. What I use looks something like this:
1.epsom salt bath–least invasive; helps remove toxins
2.heat pad–easy to perform; passive
3.foam roll–trigger point therapy
4.stretch– active isolated, pnf, static
5.integrative strength–re-introduce muscle to correct movement patterns
Flexibility isn’t typically something that people list high on their goals, although it should be. When I put programs together for people, I keep in mind two important factors 1. pain tolerance 2. willingness.
hope this helps,