Most of my work is done using sharpie markers, pencils…
… a ruler, squares, and a small engineering stencil.
I mark out in pencil all the line work first. I like using circles in my work.
Using the compass and ruler I can make a circle and I can inscribe within it a regular polygon with 3, 4, 5, 17, or even 51 sides (also double any of these numbers, and double those, etc.)
A line segment of any whole number or fractional length can also be constructed with compass and straight edge, as well as various other tasks.
I tend to play around with the line work until I have something that looks interesting to me, making circles, portions of circles, lines, polygons, and whatever else I feel like.
Color is my weakest aspect. I try to pick interesting colors to use, but I’m almost never happy with my choices…
Once colors are chosen, I shade and redo the line work in sharpies.