When I'm not working on toned paper for sketching, I like to use ballpoint pen:
It really forces you to be choice with the lines you put down. I admit that for these first two sketch portraits, I started over from scratch after making just a few bad lines. Typically, I would continue the sketch, but likenesses are unforgiving of stray lines.
What helped me create a better likeness of my subject was approaching them as caricatures, oddly enough. Try as I might, I found it challenging to create the intense
exaggeration of proportions typical of caricatures on the faces of my
subjects, so I knew that I could go pretty far in my mind to exaggerate
these portraits and end up with a portrait that is very close to the
actual facial proportions. This mentality helped me keep looser and bring to the front the unique parts of their features, which might be rendered invisible if I tried to copy the photo from top to bottom.
Another unusual method that I found worked for me for producing better likenesses was proceeding from one section of the face to the other instead of building everything gradually. I was able to space the various parts of the face more accurately this way than in my earlier attempts to put crossing lines to indicate the symmetry of the face. Unfortunately, this method made it harder for me to pick up the natural asymmetries of the face. However, in most cases, one should not start from one end of the paper to the other lest you find yourself with limbless figures. In this instance, a loose outline of the head was all that I needed before detailing.