You probably aren't surprised that stretching came in first place. It's the best thing you can do outside of yoga to get more flexible.
Dynamic stretching is a way to stretch that involves making the same moves over and over again to improve flexibility and range of motion.
Part of your stretching routine should include static stretching.
To improve your flexibility, stay adequately hydrated.
Warm muscles are more flexible than cold ones, which is why people are told to do static moves after working out.
Your yoga practice has taught you the importance of mindful breathing. The same concept applies to stretching.
Most people have some parts of their bodies that are stiffer or tighter than others. Find these spots on your own body, and when you stretch, pay extra attention to them.
Pay attention to what your body tells you. Hold the position where you feel pressure. You should feel tight, but you shouldn't hurt.
Massages can help you become more flexible if you get them often. Find a massage expert who knows how to give sports massages.
It can be upsetting to feel like you can't do yoga as well as you'd like because you're not flexible enough. But change won't happen quickly, just like most things in life.