Well believe it or not it was more obvious than you may think. Your first sketch was somewhat better just in it's proportions than this one, this one is off significantly...but I think you realized that. Why? Because I look at the face and see the evidence of someone who is at least peripherally aware of the need for proportion.
As Dom said you need to work on your basics, get those to a level where you're not guessing at what needs to go where before you move on to lighting and shadow. Though you could easily practice lighting at the same time by doing separate exercises for each one. Really I would suggest finding some art classes somewhere...for beginners, where you could receive some individual instruction.
Also go find Andrew Loomis's "Figure Drawing for all it's worth" ....just type his name into Google and you might be surprised what you get. Read them. Do the exercises. Read them again. Observe....everything. When you're walking, sitting, at a store, at the mall. Start paying attention to why things look they way they do....what causes it, what changes it, what colors are involved, where is the light source...you can even do this around the house.
Oh...and keep drawing.
Wizard's First Rule