Q.Potting Soil Ingredients
What should we look for in commercial potting soil? What are the best ingredients?

Certified GKH Gardening Expert
The best ingredients are well composted materials that are specific to the plants that you are trying to plant at the time. Although an all purpose potting soil is just fine, the best soil for your application will take some research on your part.
You will have to find out what the plant grows in naturally and mimic that to the best of your ability.
Simply put, this does not have a simple answer, as all plants will have different requirements.