Supta Pawan muktasana is the best anti-flatulence pose. Vajrasana before and after meals also provides relief. There are some life-style reasons that cause flatulence. Check the list I give below to see if you are contributing in any fashion towards that: chewing gum, talking while eating, not chewing food, eating too fast, or having a high vata dosha (which means certain foods must be avoided -- a net search should give you the sort of foods that vata doshas should avoid).
