Sitting outside thinking about what I am gonna do when I stop smoking to keep myself occupied. Here's a list. Yo-yo, play the recorder, totem tennis, shoot flies, play battleships, keyboard. What's your suggestions?
Collage, crochet/finger knitting, gardening, experimental baking, revive macrame, try sculpture, adult colouring books, word/number/jigsaw puzzles, hook rugs or embroidery, become a meme lord, millinery, furniture restoration, darts, shoot some hoops, dancing.. ok some of those are a bit silly. But with the time you'll have and money you'll save you can just about take up leatherwork, stained glass window making or anything really.
Crochet comes to mind. Easy to carry around, takes up quite a lot of hand attention and you end up (usually!) with a usable article. Also mandarins are great to make one's mouth a lot less cigarette friendly. Also peppermints but mandarins are more effective imo.