Most of it is all practice! I tend to look at some tutorials before trying to do things, such as fur, shading, proportions etc.
Shading, for instance, can REALLY define whether or not your piece looks more "realistic" or not. Should you ever want to try different styles and things, do some research and experiment! It all comes in time with practice, motivation and creativity
Looking at your works, I am very impressed! I was never really good at the style you have. Your use of colors and lighting are very nice, however, I think what would really help you is trying to add more shading to your pieces. (I am a shading fanatic). But besides that, you have really awesome art! Just explore the tutorial world and experiment to your hearts content
Find the ones that help you most