My son had awful gas and Gripe Water worked well, but we never used it as a preventative measure...but I guess we could of.
To prevent the gas (as much as we could) we would do knee to tummy presses a couple times while feeding him, as well as used a rice bag heater. My sister made it for us! :)
If you don't know what it is...it's a cloth bag (some people use a adult sized tube sock) filled with uncooked rice. Heat it in the microwave for only about 5-10 seconds at a time. when it's warm (not hot), place it on the baby's tummy while eating (over baby's clothes). The heat helps break up the gas.
Another great, natural solution is Infant Massage!