Question on the eyes for you... When you draw some one with a 3/4 profile Where do you judge the distance they should be apart from? The edge of the eye that is hidden by the bridge of the nose or the center of that eye???
Hah- if there was a simple answer for that, we'd all be doing perfect 3/4s Measurements aren't a huge problem- its the shape that gets you.
If you can think of the nose as a 3d shape, the eye begins right above where the wing of the nostril would end. Its Kind of hard for me to explain... My suggestion is refering to pictures of people doing a 3/4 turn insteed of learning without a true referance.
Concentrate on getting the front right. I didn't get beter at 3/4 til I solidified the front. Once you get that, then you can invision it easier on an angle Unfortunatly, there is no short cuts with get art *right* Just advise. The best way of learning is giving it a go, and learning the correct way.
*sigh* I suppose your right, I just think people look more interesting from the 3/4 veiw. Practice, practice, practice though and I'll get to it eventually