When I gave up soda, I did it by drinking water-- every time I went to grab a soda, THOUGHT about grabbing a soda, or even SAW soda, I drank a glass of water instead. After a few weeks, I was off soda for good, and onto a healthy water habit.
My partner gave up soda by switching out his soda with seltzer water. You can buy it in a variety of flavors (usually in the soda aisle or water aisle) and it's a GREAT alternative if you still want the fizzy comfort.
You can usually find seltzer water in 12 packs or 2 liter bottles at your local grocer.
You may also find tonic water, which is seltzer with added sodium.