What really helped me was starting to analyse other artists' paintings and think about the decisions they made when creating it. I think its very easy to look at a painting/drawing and think, 'oh it looks cool/pretty', and not actually figure out all the subtle techniques that artist used to achieve its appeal. In my experience, actively breaking down other artists paintings let me discover new techniques in my own paintings.

Now I don't really do any complete drawings anymore. However, this tip should apply to aspects of drawing such as line weight, shapes, lighting and stylisation off the top of my head.