uncountable countable nouns?

My biggest challenge in the English language is to understand when and how to use the indefinite article. I know that I need to use the indefinite article for a single noun that is countable. But some of the nouns are not really countable, but still require the indefinite article in front of them. For example...

an education
an environment
a phenomenon
a [fiduciary] duty
a conflict [of interest]
a [full] disclosure
a majority
a breach [of the duty]
a demand
a right [to inspect]
an asset

How do I know which noun requires the indefinite article if it is not really countable?

duplicate post.
(Please don't do that!)