this is a tutorial I found helpful for stuff like this back in the day
link.
There are more efficient and expedient (advanced) ways of doing things like this but it's a good little tutorial none the less, especially for the beginner to intermediate level.. roffie photoshop 3.05
gran you need to put more planning into your sketching.. I can remember the exact ratios or anything but the proportions are out in ur sketch.. do google searches for character/portrait sketching tutorials.. sketching isn't about drawing the perfect line each time its about building up from a solid base..