The eye goes where contrast lives. ποΈ π
If you want the viewer to look somewhere SPECIFICALLY in your art, put your strongest light-dark contrast there. This can be done in any medium.
Check out the art attached and notice where the most contrast is placed.
You're the artist...aka YOU'RE THE DIRECTOR;) You lead the viewer's eyes.
Try this today on your art (an existing sketch or new sketch): Choose one focal point and make that area the sharpest and most contrasted part of your drawing. It doesn't need to be over the top; it can be super subtle. Try it out and post in the comments!
( and remember this only as a rule...and rules are MEANT TO BE BROKEN! ;)