When drawing, particularly portraits, it is always best to work from life if possible. There are times when it is not practical, or even possible. The images below were created from a photo taken on my iPhone.
Gather your drawing supplies, and get comfortable in a location with good lighting.
To begin, decide on the size you want to make the completed drawing. How do you want it to fit on your page? Begin making marks for yourself as notes. You can always come back and use those notes as they are or change them, to work better with the project. Remember it is only pencil and paper.
Then block in the basic shapes with charcoal or a very soft pencil. The softer graphite, the easier it is to erase and/or lighten. Keep in mind the correct facial proportions and placement. It can help to look at the drawing from other perspectives, such as upside down and/or in a mirror, to see any errors in proportion.
Remember bones and muscles beneath the skin are what give the face its shape.
As you build up the values on the piece, it helps to take out the extremes from time to time and build it back up again. One way to do that is to use a soft brush in areas, to soften and develop it back. In the end, it will give your piece a bit more depth.
Continue looking at the drawing in a mirror and from different viewpoints, checking your work’s values and proportions.
Do not become too focused on one area too soon. It is good to move around the surface of a drawing; it helps to keep it cohesive overall.
Finally, take frequent breaks so that you can come back to the piece with a fresh eye.
Take a simple photo of your own and practice. Pay attention to the proportions, values, and shapes. Most of all take your time and enjoy the process!