How to ACTUALLY Improve Mobility
Mobility training is pretty simple. Improving range of motion in a joint is about exposure, so the simplest way to approach mobility training is: spend more time in the position that you are trying to achieve. Make any alterations that you need to get there (like elevating your heels in a goblet squat, for example), and do it frequently.
I find that a lot of people begin training with a goal of trying to increase mobility or reduce stiffness. In my experience, strength training through a full range of motion does a lot of work. That feeling of stiffness/tightness/limitation that’s felt is often related to strength, and getting stronger can help alleviate some of those feelings.
For instance, if you’re trying to increase your capacity in an overhead position (standing with your arms overhead, biceps beside your ears, and with minimal arching of your low back), then spending more time in that position will help. Exercises like dead hangs and scapula pullups are a great place to start, but building strength in the overhead position through exercises like lat-pulldowns and landmine overhead presses will help you to progress to more challenging exercises like pullups and dumbbell overhead presses.
Bodyweight modalities like Animal Flow are great for building strength through non-repetitive ranges of motion, and make for a good supplement to regular weighted resistance training as well. Yoga and Pilates are great also, but I am certified in Animal Flow, so I am a little biased.
Spending some time doing targeted stretching is great. But when you take your body through a full range of motion under load, I find that's where the lasting mobility gains are made.