How to: Plan your design on paper (figuring out how many snowflakes you want, and where), then mark it on a wall. Punch circles out of card stock with a circle craft punch. For a wooden or textured wall, place thumbtacks where you want the dots to be, put a piece of removable double-sided tape on each tack, and place your dots. For smooth surfaces, put a piece of tape on the back of each dot, and place.
Get it: Supplies for all these projects (craft punches, card stock, tape) from craft stores like Michaels.