Begin by roughing in the contour line drawing of the object.
Lightly and evenly apply a medium tone over the entire object. Notice the right-handed angle of my pencil strokes. You are just "coloring in" the object to establish a beginning point with the shading. I also darkened the outline a little at this point.
Now use a kneaded erasure to remove some of the graphite and create the highlighted areas of the drawing.
Except near the highlights, apply another light layer of graphite over the entire object at slightly different angle. You can see how this works in the example below. This will blend the strokes together creating a more even tone and darkening the object a little more.
Draw in the outline of the cast shadow and evenly fill it with a medium tone. I also shaded in the shadow coming off the stem at this point.
The last stage of the drawing is where you look at the object as a whole, trying to fix problem areas. Look specifically at areas that need more transitional blending and areas that need to be darker or lighter. At this point I cleaned up the outline with the erasure and darkened it in again. I also darkened in the stem, the core shadow and certain areas around the edge of the object. I felt confident that I fixed all the problem areas, so I considered it finished. Try not to go back in too much to make it perfect. It's easy to over-work a drawing when you do this. It's better to get it to a point where it looks finished and leave it alone