The first thing I do is to mak a sketch of the basic shape of his head, which in this case is a egg with two eyes and a big mouth.... or very close at least :) I measure with a ruler to get the edges of the eyes, nose and mouth in the right spot. I make measurments from different spots and compare the original with the drawing I'm making. If you have a photo in the size of A4 and want to upscale the drawing to A3 you just multiply the all measurments by 1,5 for example. when the porportions is right I put a base shade on his face and smoth it out with some soft paper. Then I start with the eyes which in this case is black so very easy. Just remember to leave one or two white spots in the same "corner" in both eyes.

I start drawing his smile wrinkles and wrinkles around his eyes. To fade the lines out I use a paper stick almost like a pen ( you can see my equipment later in this post). I also start to shade his left side more darker. For the wrinkles and darker areas I use a graphite pen with softness of 4B, sometimes 6B. For the brighter areas like the base shade and other brighter parts I use HB and 2B graphite pens. I sometimes use my eraser just as much as my pens, especially when I want to make a smoth fade from white to black.

Now its time to start with the details like mouth with teiths, his nose, eyes and eyebrows. For this I mostly used a mechanic pen with thickness 0,5mm and one 0,7mm. These are very handy when you don't want to sharpen your pens every 3 seconds. For the shading of his lips I used a HB graphite pen.

The drawing is now almost finished, the only thing left is his shirt. It was white in the original with gray background but I decided to make it dark because my background is white. I didn't use as much time as would like to make it perfect but I decided to make it simple but you could still tell it's The Rock.
Below you can see the finished drawing.

This is some of the equipment I used for this drawing, the thing that is missing is a ruler.