This is really fun to do because you can use a bunch of different kinds of doodles and they all come together to make a really nice piece of wall art. You could do a color scheme like I did, or make a colorful, rainbow square-doodle paper. I colored this with purple, blue, and green gel pens. I got some doodle ideas and I think even the whole square-doodle paper idea from this doodling blog: https://doodleaddicted.wordpress.com/
The hardest part about making this is making the squares to put the doodles in. You might be able to print off a template for this somewhere, but I just did it by hand by measuring it off.
You could also do this in random circles across the page or put the doodles in outlines of hearts or whatever you want.