Lesson 2: Contour Lines, Texture and Construction
Start off by drawing a curve on the page. You may want to practice these a bit on their own as well. Try to draw a curve that bends and turns a little. S-curves are usually generally pretty good. Put yourself in the mindset of drawing in 3D space - your curve isn't simply sitting on a flat page, it's travelling through the depth of it as well.
Next, draw the same curve a little below it. This can get tricky, since it's quite difficult to replicate an identical curve. You may want to build this in segments, but make sure that these flow smoothly and flow directly into one another.
Also, try and consider perspective - the space farther towards the back end of the arrow is going to be more compressed than the space up front, so all of the distances get a bit smushed. The arrow's width is going to be smaller back there, and even the space between different lengths of the arrow are going to have less space between them.
Finally, add a little bit of shading at the bends, and reinforce your overlaps with a bit of extra line weight. A good rule of thumb for applying line weight at overlapping points is that the line that crosses on top gets the thicker treatment, to establish its dominance. Don't go overboard with this though, just make it a little bit thicker. Be subtle.
The purpose of this exercise
This exercise is all about familiarizing yourself with all three dimensions of space, and getting used to plunging into the depth of the scene, rather than sticking to just the space defined by the page itself.
Mistake: Being afraid to let your edges overlap
Sometimes students are a little afraid at first about letting their edges overlap. This is going to make your arrows look very flat, and is part of getting stuck thinking as though you're working in the space defined by the page, rather than a three dimensional world where your arrows are free to twist and turn.
Mistake: Not applying perspective
While this arrow certainly does look three dimensional, it's still pretty limited to the space defined by the page. You need to let it push into perspective and explore the depth of the scene and apply foreshortening (making the farther end smaller and the closer end larger).