My first selfie! Can't say I enjoyed doing this, painting values - ok, but trying to draw myself from life was one of the most frustrating moments of everything art related I ever did D:
Mass light/Mass Shadow - my light source was a window, and as it was gettting darker my painting assumed a more low key aspect, making the mass lights and mass shadows similiar in value than if I was using a spotlight. The mass light is takes most of the left side of the face.
Half tone - As I didn't use a direct spotlight the haltones were dominant. I think halftones are the most important to give what you're paiting a sense of 3D
Highlights - subtle highlights only, mainly cheekbones, tip of the nose and cupid's bow (I have no idea if that's the word for it)
Fill Light - on the right side of the face, concentrated on the edge of the cheek, brow bone and the hollow(?) of the eye
Core Shadow - edges of the eyes, nostril
Cast Shadow- I think I could've gone bolder on cast shadows, more spcifically aroud the nose, to really show there's an edge there.
Nice work for this being your first go at this. The mood is also very good. My main input is on the values as they are a little bit spotty. Using brushes that match the size of the plane on the face that you are observing will help. This looks good so far. I would recommend taking a look at sargent's and velasquez paintings to study the brush stroke directions that define structure, including the head and the neck. Notice the various size of the brushmarks and the directions they flow. If you use too small of a brush it can feel overworked. If it is looking spotty you can also run a blur filter on it and then tighten up the features after that.