Improving isn't easy and you have to push yourself to discover techniques and methods that make your writing better.
So here's my first answer: Never stop learning.
Second, read and analyze other writers. Ask yourself why something works (or doesn't work). I don't consider myself particularly analytical but I still read and have an interior dialog with the authors. Occasionally, I'll read an awkward sentence and say to my invisible author, "How could you let that get past you?" Sometimes, I smile and then say, "That was an excellent paragraph."
Third, start or join some kind of group where you edit each other. I no longer do that, but it was an invaluable part of my growth for the first twenty years. Even after I had published enough to make a living, I still shared my work.
The last group I started, called the Scriptiques, made me realize I was ready to go it alone. For several meetings, they had made what I refer to as copyediting suggestions—often helpful—and all of us realized it was finally time for me to move on.
I want to improve my writing,
so I continue to find ways to develop my skills.