I don't like the idea of a full on tutorial, as I truly believe that no one can follow another's footsteps. But I will explain how I've achieved this portrait, step by step, in the hope that it will inspire and encourage others to do the same.
First off. Get your sitter into the right position. That sounds easy, but it isn't. The best position is usually 3/4. Think about it. Full frontal and you (and your final viewer) has no real idea of bone structure. 3/4 view and you've got the nose and the cheek and the jaw - this applies to caricature as well.
Now start sketching. From every angle. You need to understand how they exist in their space. You need to know and feel what they are about. I once worked with a great artist who insisted on sculpting every portrait before he began work on it - for him it was the only way to understand the skull beneath the skin.
Work out your lighting. I chose light from the left and it seemed to work. As your viewer will read the painting from left to right (we all do) then this is a nice logical approach. It gives a feeling of relaxation - if it was lit from the right it would have a very different, even uncomfortable feel...try it.
Now take your photos. These are what you will work from mainly.
Now sketch up the photo to full size. My canvas (pre prepared with gesso) is about 3 x 4' , so pretty large. I played around with composition, but didn't take long to sort it. I wanted a medieval/Renaissance feel to it, so the positioning of Claire was important and set everything else. The arch behind her was vital. To her left will be a mirror with her boyfriend James (my son) in it. For a nice feeling of wow, I'm going to light him from the other side - completely impossible. The intention of this portrait is to be personal, so her 2 cats are in the pic and behind will be Bournemouth Beach (part painted).
OK. so now you're ready to paint. I'm using acrylics - quite a mix of makes! I get a lot of them off ebay from people who've tried and given up and etc - much the cheapest way to buy.. Mix up a nice Van Dyke Brown, Sepia or Dark Umber with water and paint watercolour style to set your tones.
Now you can start painting. I started with her left (our right) eye and filled out from there. I've only done the right side of her face, although you will note the rest is still quite accurate for tone if not for colour. I can't tell you how to mix colour - you need to play. But I used a Venetian Red, Quinacridone Deep Purple, Deep Turquoise, Golden Ochre, Titanium White and Cad Red for the flesh tones.
Will put this up as I go and hope you will find it interesting!