Study the work of other artists, past and present. Find subjects for your artwork that really interest you. Make lots and lots of pictures. Try different styles and mediums until you find the one that is right for you. And, most importantly, have fun.
Some illustrations go very smoothly and others can be very frustrating.
Sometimes I get stuck because I can't figure out the composition or colours to make the best illustration. When this happens I end up doing more rough drawings than usual until I am happy. Then I can proceed with the final drawing that is printed in the book. I drew my own comic books and my parents always encouraged my artistic efforts. In art college I studied art history, and focused my interest on the work of famous book illustrators that I admired.