Look at yourself in a mirror and, … draw several five-minute sketches of your face describing different angles of your face and head.
I did two with just one mirror and two with two mirrors to get different angles.
Draw five more quick sketches concentrating on the overall shape of the head without the neck.
Draw the shape of your neck repeatedly …
This third exercise had me puzzled. Why the neck? Surely the eyes (in particular), nose and mouth are far more significant and need practice rather than the neck. I had to remove my shirt so I could see enough of my neck to draw. Once I’d finished, my shirt went back on and most of my neck disappeared.