Grid paper

Print your own graph paper:

• https://www.waterproofpaper.com/graph-paper/grid-paper.shtml
• https://incompetech.com/graphpaper/
• http://www.math-aids.com/Graph_Paper/

Purchase graph paper:

• https://www.officedepot.com/a/browse/graph-paper/N=5+549824/
• https://www.staples.com/graph+paper/directory_graph+paper

See Math Font Keyboard page for electronic grid software + keyboard

Image from http://nicoleslearninglab.blogspot.com/2015/02/bright-idea-using-graph-paper-as-math.html