When making drastic changes to your own range of motion there is only one person you can trust: yourself.
No one knows you better than you and I'll be damned if I ever think that I know what's best for anyone. I can only teach off experiences that I have had myself and the people that I have worked with. I am STILL learning new stuff and tinkering with things that are effective and things that are more enjoyable but still give good results.
The main question you've got to ask yourself is: Where are you starting from? Are you as flexible as a steel post fixed in concrete, or are you a rubber band flowing in the wind? Generally most people are the steel post, that doesn't make the rubber band the goal: they both present different advantages and disadvantages. You have to think, what do you want to be flexible for?
Certain disciplines actually rely on a lack of flexibility
For me and the people I train, I want us to have the movement capabilities to have MORE OPTIONS to do different things. However certain disciplines actually rely on a lack of flexibility - creating forced stability in situations requiring crazy amounts of strength or power. If you want to specialise, something has to suffer.
Back to where are you starting from though. If you are still a wee nipper and haven't been too banged up from years of eager training, you just might be lucky enough to be able to make quick adaptations and go on your merry way. If on the other hand you have been stiff as a board for twenty plus years and then tried to get fit, you're going to have a bit of work to do to get back to neutral. Oh yes, there is minus flexibility points, I invented them.
I have noticed a trend with personality and flexibility: if you are a highly stressed, over-thinker with breathing dysfunctions, chances are you'll be a tad tight. Jimmy the stoner though? Not so much. I bring it up at my seminars all the time. Do you ever notice that when you do happen to get an injury or niggle it's always when you're having a really shit time at work, or really stressed out? It's like it's the LAST THING YOU NEEDED TO HAPPEN when you want your training to go well more than ever. Your ability to move is directly affected by how you feel. If you want better mobility, you also need to learn how to relax and breathe, then your efforts will be twice as effective.
Starting off slow is the key, little bits every day of self policing is the safest way to go
If you are going to make dramatic changes to your own flexibility then I would structure your programming around that, make it your sole focus. There is no real point doing a wee bit here and there and keeping on doing what you have been doing, your body will get mixed messages. It isn't hard to research how much range of motion is ideal for most body parts - provided you don't look up "How to be a contortionist", you should be ok.
Starting off slow is the key, little bits every day of self policing is the safest way to go. If you have been working with a specific area for a ten to twenty minutes one day then wake up the next day with a bit of pain in that area, then you know to back off a bit. If you are ok and feel awesome, then you know you can push it a bit further. Depending on how well you react to neuromuscular training, you may keep a good amount of the improvements you made over that session or you may only be left with a slight improvement - key word there in both scenarios being improvement.
If you have been weight training or active in any way with any limitations then you MUST scale back your training. For example increasing your squat depth or your shoulder flexion and then continuing straight into using the same weights as before is a recipe for disaster. Taking the time to rebuild your new found range of motion and refine your technique will do you no harm and if anything, make you a better athlete. It won't take you very long to get back up to your old numbers and you'll be very pleased when you surpass them easily. A little bit of extra body awareness goes a long way.
Whatever method you pick to work with to increase your flexibility, do devote some time to "playing" with your newfound range of motion. For exmaple if you are working with your ankles, do drills with your toes and rotations; see what happens when you block off your knee or increase the amount of flexion. As silly as it may seem, it is those things that will build up how well you can stabilise yourself and keep your newfound range.
Pick a body part and say to yourself "What do you do?" And see if it does the same as the other one, if not, can you fix it?
