Great question, and it's kinda our thing so we're glad you asked.
First of all use a SodaStream sparkling water maker :)
Then make sure you use very cold water to carbonate. Cold water from the refrigerator holds carbonation much better than cold water from the tap.
Next, sparkle the cold water with your favorite kind of fizz, from a gentle bubble to a full on bubble blast.
Finally, add flavor if you'd like to and pour yourself a glass of fresh bubbly.