Come up with an idea: What are your interests? Love flowers, animals, movies, baseball? Choose whatever your fancy is and that can be the theme for your board game. Combine ideas if it would make for a fun game.
Make the board: This can be the really fun part. The board itself can be made of anything and you don’t have to buy special items. Make it from paper, cardboard, wood, plastic — anything!!! We did this for Girl Scouts and the girl who planned the game boards for our troop used two sheets of paper taped together on the back side. She planned a path on the paper with simple line drawings of flagstone. The simple design, as well as the large amounts of white space, enabled the girls who made the games to decorate to their delight. You could color the board, mod podge stuff on it, put stickers on it, or just write the important words. Remember that most players like to have a “Home” space and a “Finish”.
Assemble the parts and pieces: Cardstock cut into ATC sized pieces (2.5″x3.5″) make excellent cards. Pieces can be flatten glass marbles, little animal erasers, pewter knick-knacks, coins, Legos, Kelly dolls, Littlest Pet Shop animals, or anything you can think of. I love the idea of using Matchbox cars for a car racing game.
Write up the rules: This is your game, so the rules are up to you. Remember that your fellow players won’t be happy if you change the rules midway through. This is only acceptable on your first time through or so. Be sure to write those extra rules down immediately when a problem in the original rules is found.
Try it out: Be flexible and have fun! If it’s not the perfect game, make another.