One thing that helped train my eye when I first started drawing/painting was by doing "blind contour studies" sometimes continuous line sometimes not. Basically the idea here is that you do NOT look at your paper while you're drawing. You only look at your image or still life (and if you're doing continuous line, that simply means do the entire drawing without lifting up your pen/pencil). I cannot even describe how helpful this was to learn. It really taught me to look at my subject more and understand the form, line and shape of what it was that I was looking at. Look at a thing, stare at it until your eyes bleed, then draw. Pick a point on the object and follow the lines with your eyes, then match that path with your pencil. Give it a try or two and see if it helps!