First tip, make the background like blended and blurred, and from that background make a dark and a shine side, you can get the points from the drawing you made, try to use different colors to shade and also don’t use black to shade, and use a real image as reference, if your drawing is black and white then you can use black to shade, you can use a circle to learn how to shade, and watch YouTube videos too, with that you can make really realistic drawings, and you will have a lot of experience I’m drawing, and you will know how to shade correctly in other styles like cartoon or anime, those are all the tips I can give to you.