The following suggestion have been practised by me at some or the other stage in my life and found to be very useful. So I am listing them here.
Hot water helps to clean your stomach. Take a cup of hot water either soon after brushing your teeth in the morning or at the time of going to bed in the night.
Drinking water in the morning as soon as brushing the teeth is so helpful in preventing acidity developing in the stomach and keeps it fit for the whole day.
Omam and Jeera, half a spoon of each in warm water, taken sip by sip cures from indigestion and stomach upset.
Take half spoon of dry ginger, a pinch of turmeric, half a spoon of palm candy, a pinch of pepper powder and either jaggery or sugar, small quantity in 150 ml water. Let this boil for about 3 minutes. Drink this concoction slowly. This will cure cold and sore throat.
Drinking buttermilk with either Jaljira or fresh curry leaves keeps the stomach free from acidity.
For heart burn due to acidity one can have a small amount of Fenugreek powder mixed either in water or bittermilk.
If you are feeling heavy after a meal try Dabur's hajmola. It really helps!. As one ages, the digestion gets slower.
Of course, meditation and yoga are great healers. Kapal bati is particularly helpful to keep stomach (madhya pradesh) under check.
Another very effective general remedy has been suggested by Art of living Sri Sri Ravishankar ji. I have practised it and it helps to take care of bad bacteria in the digestive system. Take 5 to 6 pieces of cucumber in about 150 ml water and soak it overnight. In the morning squeeze a few drops of lemon juice in it and drink this on an empty stomach. This is called alkalinising the body and is very effective.