My advice is to try to draw bigger portraits. Your lines are struggling to define shapes and traits of the face. Also you should determine and choose the better tool that makes you feel comfortable. For instance: the portraits made with black ink require a bigger format because line are not showing us the shape of the face clearly. It doesn't matter if you choose pen, pencil, felt tip. Just draw. After that, you should analyze the general shape and his volumes. At artwod you'll find splendid tutorials to improve that. And do not rush to sketch the face or the portrait before you understood the head. Some of the lineart is very expressive, but sometimes is too much. I recommend you a bit of line economy (that means if you can define the one part of the head with one line why bother with more?), | Artwod Feedback