I used to drink a lot of soda, but I'm not as tempted since I bought my Sodastream machine! I bought the Crystal Light Lemonade syrup for it and it gives my all the delicious fizzy goodness for only 5-10 cals a glass. An average glass of soda is over 100!
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.
Though you really can't do this when drinking from a can or bottle, at a restaurant they can and will do it for you OR you can do it on your own if you're at a fast food joint. Fill half your cup with regular coke and then the remainder with diet coke. You really can't tell that much of a difference and you've just cut the calories in half! And because the regular coke goes in first, it's what you taste the most of. I used to drink 6 - 8 cans a day and this has really helped me cut down.
I will admit that I am addicted to Coca-Cola. Diet Coke tastes DISGUSTING to me and Coke Zero is a little better, but still tastes weird to me. Recently, I discovered Diet Dr. Pepper. It is really good and doesn't taste diet-y at all! It really helps take the edge off my soda cravings and I don't have to worry about calories at all!