I've never quit entirely though I'd like to...someday...but I have cut back a lot at times, and my #1 tip for doing so is to drink soda water. I have a sodastream soda maker and I make bubbly water and add a little bit of juice, lemonade, or sweetened lime juice to it. It has waaaaaaay fewer calories, no scary additives, and it definitely satisfies the carbonated beverage craving.
I'd also recommend that you don't quit cold turkey if you're a more-than-one-a-day soda drinker, but to gradually reduce to once a day before you quit! You'll be more likely to succeed that way, I think.