It is a good idea to try this as an exercise to change the way that you look at things. By working upside down you draw only the shapes you can see and not what you think should be there.
Caroline started by using this photograph pinned upside down
You can, if you prefer, simplify things by splitting the photograph into four to help you in positioning.
Using a 7B pencil she first drew an ellipse ( representing the tabletop ). Using this shape to work from, she went on to put in the oblong shape underneath and the black square to the left of that. From there she entered the curves which take the eye down from both the square and the oblong to the bottom. She continued in this way, plotting in the main larger shapes.
After all the main shapes were done she moved on to the more intricate parts. This is done by paying close attention to where things are positioned relative to the other main shapes already done. This really will hone your observational skills.
Finally think about adding tonal value. Caroline used an 8B pencil to shade in the darkest areas first then the lighter areas using a variety of hatching and crosshatching.
Only when she had finished did she turn the drawing the right way up.
this was a very good representation of the original photograph