I tend to use ink pens for leisure sketching and for test drawings that may be developed further if  I like the progress of the picture.  You might consider my ink drawings as my first-idea sketches.   Also, since the ink cannot be erased, I am forced not to rely on erasers to create a good sketch.  The eraser is an important tool in your drawing kit but it must not be relied upon to keep your artwork accurate or clean. 

Learn to sketch clean and your finished product will likewise be clean.  I do not however, recommend that you sketch with an ink pen.  I do use a pencil when I start a sketch that I intend to become a finished drawing.

We begin by looking at the photo from which the sketch was derived  in Picture 1 after which, we see the final sketch in Picture 2.  If you look closely in Picture 3, you will see the guidelines of the girl's frame drawn very lightly.   I have highlighted those guidelines in Picture 4.  Click on any picture to see a larger image.   Practice making your initial guidelines as light as possible.  They should be barely visible to your eyes.  Remember they are only guidelines and will not be a part of the final drawing.  If they need to be erased later it will be easier to do so and will make a cleaner drawing if the guidelines are drawn in lightly.  

Sometimes I draw my guidelines so lightly that I do not erase them later but rather, I may use them as part of something in the final picture.  Other times, the final shading may cover them up.  It is always best to use the eraser as little as possible.   In picture 3, you can see the actual initial guidelines.  I have purposely darkened them here so that that you can see that the initial guideline takes on the same pose as the final drawing.  The initial guideline should show action.  It is the real life of the the picture.  If the guideline does not come alive, then most likely, the final picture will not either.

Notice the dotted lines on Picture 8.   I noticed that I did not draw in the left arm correctly and was not aware of its true shape and position as most of it is hidden by the body.  The dotted lines show the correction for the left arm.  Notice also that even though a part the figure will not be seen in the finished drawing it is always good to lightly sketch it in so that you can keep the visible parts of that element in proper perspective.   Picture 9 shows the completed drawing with the stripes added.  Make sure that the stripes follow the contours of the body.  If done correctly, it is the stripes that add so much to the effect of depth and dimension to this drawing.  Examine the striped ball and vase examples in section one.