I just cracked the spine on my latest design journal. I've been keeping a design journal for at least 6 years - after I finally decided that the scraps of paper method just wasn't working for me. I usually fill two or 3 books a year with sketches of course, but I also use it for business to-do lists, supply lists, an occasional grocery list, and doodles. I doodle when I'm on the phone (taking notes) and especially doodle when I get stuck and need something to spark my creativity.
This is a design sketch that ultimately became two watermelon tourmaline pendants.
This is a doodle that helped me resolve the focal point of one of my vintage Mardi Gras bead necklaces.
Can't see how this helped? It's in the eyes: on all of the strands of Mardi Gras beads I have, there was only one eye bead, and it fit nicely inside of a frosted glass donut bead.