Find cause. Many babies have gas...Especially in the evening. If the gas is a lot and the baby is fussy, i like to address diet. Other things that can help with gas include gripe water, a product called cocyntal at the health food store, and for some just probiotics. Sometimes pumping the legs gently like a bicycle will help the baby release gas. Massaging clockwise around the belly button helps move gas.
Flatus. By burping more frequently, although this isn't going to help too much. The gas comes from the foods you are feeding, such as lots of green veggies. Gas isn't a bad thing other than the smell. Baby could also be swallowing too much air with feeds.