I think a lot has to do with Blood Type as well.I thought it was a bunch of baloney till I actually got a book about blood types and read it-hit the nail on the head.I'm type A,which is super sensitive digestion,triggered by stress and emotional upsets.I avoid high acid foods such as lemon,oranges,peppers,also all processed foods! Soothing teas in the evening with honey are good to settle your stomach down,as is a nice relaxing walk to get things moving.Oats have long been known to benefit digestion,minus the acidic affect which oranges have (also good for digestion but due to their acid content).Warm oatmeal with honey is a good way to loosen things up.
Make sure you drink enough water as well.
Foods that have always given me trouble:
processed foods such as spaghetti,veggie burgers,cold tofu,tempeh,beans,rice,popcorn,sugary desserts (seriously, a date is such a better option than cheesecake!).
Yogi Tea makes a really good Stomach Ease tea which I've used time and again! If you get queasy,have some peppermint tea.Above all,avoid caffeine! and meat,and dairy! Those are horrible for your digestion!