Think about one or two elements while you're doing these--proportion/drawing, value grouping, color mixing. The benefit is in "thinking with your brush" rather than trying to rationalize. Every bit of practice establishing correct figure proportions will help when the time comes to work from a model.
If you don't have a model or any suitable photos, grab a fashion catalog. Put up the photo and look at it as if it were a model, not right beside your canvas. Try to get the gesture and proportion.
This one is my all-time favorite, but there are many inexpensive guides (like $4 or less) also available which will get you started.
And remember, if you paint from a copyrighted photo which is not your own, it should be attributed if made public. These last two studies are based on images from a Hanes catalog.