learning portraiture

i made an attempt at doing a portrait of heramb. when i do a portrait, i seem to get the drawing and the under-painting pretty close to the subject but i don't do any good from thereon. i guess it will take me a few more canvases to figure out how to approach and do portraits right. the canvas was 20 x 24'' and it was pretty big for me and even though i was a little intimidated at first the experience of working on a bigger canvas was just amazing^_^

                                                                             

portrait of my brother, keyur (watercolour wash)