How to take care of watering in Plants?

Hi all, 

My brother bought few plants with some manure like coco peat online. And we kept them in our house in the shaded area. I have planted my plants in cocopeat and vermicompost. Now we are watering them on every alternate day. He researched a bit that water requirements can be checked by finger tip method. Is this okay?

What about the quality of water, is it should be filtered or normal?