This might sound like throw away advice, but really it's simple: find people who are better at it than you are, hang out with them, and practice as often as you can. Then practice more. And when you feel like you have practiced enough, do it again.
Not bouldering, but on my bike I went from "yeah, I can sort of do jumps" to sending the biggest shit I can find in just under 2 years and all I did was exactly what I just said. The people I know who keep levelling up are the ones who do three times as many reps as anyone else.
At the trails, there are the people who sit around, chit chat, and occasionally send a lap, and then there are the people who just go non stop. For every lap everyone else is doing, they knock out 3. It's true for every sport. There is no shortcut to greatness. It's a grind. A rewarding grind, but a grind nonetheless.