Gesture drawing is the most basic technique used by all professionals for assigning proportion, composition, depth perception, and the other qualities that you want to convey in your artwork. It is how you start your picture, and one of the most fun parts. Rather than go into detail, I would suggest you research it as it is a vital skill you will need. I can recommend starting with the book "The natural way to draw" by Kimon Nicolaides. It is the artistic equivalent of freenoting and is a very loose and pressure free way to draw.
I hope this helps.