Back in college, when I took all those basic design classes and color theory, my professor was very much a stickler for precision and for even lines and such. I understand the reasons, but I could never paint as straight as he wanted, so I didn't do so well in his classes. However, I always did like the ideas that he taught, so now, years later, I finally achieved the perfection with painter's tape!
Let's get kickin':
Also, you'll need wax paper, a knife and a ruler.
First, spray paint the canvas. Let it dry.
In the meantime, measure out the grid that you want your design to be. Pink tape was 3/4" wide and blue was 1" wide, so my grid was 2" apart with 1.5" border.
On wax paper, stretch out the lengths of the painter's tape that you'll use for thin strips. The length should be enough to wrap around the back of canvas for a clean look.
Cut the tape into 1/4" strips.
Take your canvas, mark where your grid will go.
You should have the grid happening like in the photo above.
After you are done with all the squares, I recommend spraying the whole thing with fixative, to make sure everything stays put. Alternatively, you can cover everything with modge-podge.