This has been talked about including very often - recently there’s a few topics about this which have a lot of tips and information that have been suggested above. Search before attempting to create a topic just to see if your question hasn’t been asked to avoid clutter threads.
You basically just practice and start building find something your most interested in or enjoy such as. Nature, builds, weapons, vehicles, ect. Try creating detailed models or table based off a reference image keep experimenting with different styles and themes if your wanting to improve your building skills you just practice an learn.
However i’m not going to go any future since there are numerous of threads and resources which leaves a lot of tips for becoming a better builder or wanting to improve your skill.
Ah, I see my own self asking this very question on this topic as you can see. I have had improved a lot since I asked that question a while back and I had learned a few things. For me, when you are building, it may help to take your time when doing it, so you don’t miss or can be able to add details which helped improved my basic builds at the time. You can also listen to music if it helps you, especially your favorite songs or genre or finding the right type that might help you in this. Of course there are other suggestions I could mention like using plugins and other programs to help you build like Blender and such, but I’ll leave that to others to add for input. Good luck in your improvements!