Started mocking up logos in black and white before adding color after a mentor chewed me out
Used to just pick a palette first and design around it, which led to a lot of muddy looks nobody wanted. Now I nail the shape and spacing in grayscale first, then layer color on top once the contrast works. Anyone else find that designing without color first fixes a lot of weak spots?
Gray value studies changed everything for me too. Started doing quick thumbnail sketches in just black and white before touching color, and it really helped me spot bad composition early. Still the most useful habit I picked up after years of making art.