Portrait work divides into two basic areas of effort;......firstly, the satisfactory lighting of facial features, and secondly the intuitive capture of insights into the sitters inate character...(!)
Not too surprisingly the first is relatively easily learned and the second requires either great talent or a lifetime application!
The best way to learn the first is to get yourself one of those polystyrene 'heads' which are used for displaying wigs. Go to a street market and look for the 'cheap wig stall'......persuade the owner to let you have a marked/damaged head. If you can aquire/borrow a wig of some kind so much the better.. Next,...its off to the local joke shop for a pair of eyes!...if you can't get eyes with glossy reflective lenses then try a couple of marbles,...the important thing is to be able to watch highlights as they come and go in the 'eyes'.
Assemble the elements of the head .......You now can try different lighting and situations and watch the effect, or use 7D to compare results. Try placing 'Mary' in a window and see soft sidelighting,....add a paper reflector for 'fill-in' effect......place ''Mary' with rear to window for 'rim-lighting' and use reflector for 'modeling' light. Next,...get a simple table lamp and walk around 'Mary' noticing highlights in eyes and shadows etc. You can spend as long as you like as 'Mary' will not get bored or change her expression...!
The basic 'two light' and 'three light' set ups are easily learned from numerous books but perhaps the best way is to find a couple of portraits which you like and try to analyse/duplicate the lighting.
As a 'quick start' method with your two light sources,..place the brolly at 45 degrees to camera position and other,harder light behind sitter on opposite side to give oblique/rim lighting.... ALWAYS keep lighting as simple as possible and avoid dual shadows.
Once you have two or three lighting set ups that you are confident about you are ready to try to capture character,.....find a willing helper/sitter who will enter into the spirit of what you are trying to do, and get he/she to strike expressions to camera,..you will learn a huge amount from this alone.
Lastly, you should have a good look at good portraiture both in art galleries/books and also by photographers. If you can get hold of the July copy of 'Black and White Photography'...the UK mag, then you will find the superb work of arguably the UK's top candid portrait photographer, Jane Bown. The whole article including her economic working methods is very intersting to all serious photographers whatever their field. Jane has spent 50 years 'snapping' the famous mainly for 'The Observer'. As you will see, she takes but a few moments to glance into peoples souls!!
I hope some of this is useful....good luck!