Liz, I highly reccomend working left to right. I also like to work in the same manner as you, going all over the place because you get bored with one area!! However, I've found that working from left to right is more satisfying on the eye, and stops smudging, PARTICUARLY with soft pastels, coloured pencil is not so bad, but you would find the smudging with graphite and charcoal, however after previously working primarily in graphite and charcoal, I've found pastel to be even worse for smudging!!!
Also for working with fur, generally speaking I try to work from a photograph that allows me to work left to right, where I am able to layer each section of fur on the previous section, as it is in real life. So I try to start on the base coat and slowly work backwards so the hair is being layered. If that makes any sense at all!!!!
Feel more than welcome to start a thread like this, you'll find it really helps your drawing improve as you can see it from a different perspective.
In fact, if you don't mind, do you think we could critique each others work as we progress with each commission? I like to have another set of eyes to tell me where I'm going wrong, if you're not interested no problems ;)