First, try a change of food. Sometimes, something in the feed just doesn't agree with your dog. High fiber diets are special culprits! Dogs on a reduced calorie diet or a senior diet may be especially flatulent. Just try another feed for a month or so and see if that helps. Of course, you know that you must make the change over a couple of days or you'll wind up with a dog with a major intestinal upset!
Second, take a hike! Nothing like a little exercise to help move gas out and the two of you might enjoy good stroll after dinner.
Third, make sure you aren't overfeeding your dog or giving him lots of treats from your table. Too much food, just sits there and ferments - result - gas! All those table scraps might be causing intestinal distress and coming out as gas.
Fourth, don't overdo the supplements - vitamin pills and other supplements. If the dog is getting a good brand of feed, those other things aren't necessary. The exception would be something your veterinarian has deemed necessary for your dog.
Fifth, ( and it's gross!) is your dog eating feces, his or the cat's, in the yard? Get out there and clean up several times a day so he can't get to it. Or keep the cat's box out of reach!
Sixth, don't give your dog a lot of dairy products. Just like humans, dogs can have problems digesting dairy products.