Watching paintovers/critiques can be really helpful! This one goes over the usual composition, value and colour adjustments. What I found most useful though is the perspective it gave me on putting together a portfolio. He hightlighted the advantage in having diverse subject matter, camera angles and light sources to show your capabilities. I thought that this would be good to keep in mind when I’m planning my 4 concept art pieces.
Swathces (2014) [Youtube] Portfolio Review & Paintovers