first you have to find a good reference. Then you have to observe how the light works on the object.
You can also look on how others artist resolve this problem.
1- define your shape
4- highlight and reflected light
The nick "Toeuia" that I'm using comes from a, idk, you okay the chess game while chit chatting them. The first two are students. Then you know, finally, the champion, and then the champion's sensei. I played like this so many times until suddenly there's another chess master. Very naive but super smart. After he lost, he kinda advised me not to give up on chest. Because the next one was never seen beaten. Touya.
This is Krizzirk Toeuia Aeslan, I'm picking up transmission. Draftwingeds on, duty on, exhaust ready. 310 Immulicationsers approaching. I'll take the cake and----hold it!!! My Cosvere Radar detected 3001 of them!!