I'll just share what I tried. Warning: I'm not an expert... in fact, the apple above is my *first* value study ...
I had been avoiding value study for an obscenely long time myself. And then, when I decided to finally study it, I did what any enthusiastic student would do... try shading a human figure, without any reference :P. Coz.. u know.. painting apples is really boring
. Of course, I'm only posting the apple above, so you can imagine what happened to the human study
But honestly, I'm glad I did the apple. I definitely learnt a lot more with it and have a bit more confidence and understanding. So, I'm gonna try some more still life studies now...BTW, I used the method described by Andrew Loomis in his book "Creative Illustration" (available for free online, in case you don't have it already)
It'll be great if the experts can pitch in, but I just wanted to share my experience in case you're facing the same issue as me.