Been - being - bean
The two participles of the verb 'to be' are sometimes confused, by native speakers as well as foreign learners. They would not be confused so often if the writers pronounced them more carefully. Been is always pronounced as one syllable (IPA: /biːn/). Being should be - and is, in RPO - pronounced as two - 'BEE-ing' (IPA: /'biː ɪŋ/) - but in loose speech (and in some accents) is often rendered as one, so that it sounds the same as been.
Pronunciation may serve as a rule of thumb. You will be right more often than not if you say the word carefully and write it accordingly. But you will not always be right, particularly if your own pronunciation is not precise.
use BEEN after the auxiliary 'to have' (e.g. "it has been said"),
use BEING after the auxiliary 'to be' (e.g. "you are being watched").
A further confusion can exist - less often among post-school age writers - between been and bean. This can be illustrated by a reference to literature. Roald Dahl, in his children's story The BFG shows the poor education of the Big Friendly Giant by describing the favourite food of (the other) giants as "human beans" (p. 25 and passim). When Sophie, the child heroine of the story, points out that "the bean is a vegetable", the Giant replies "Not the human bean ... The human bean has two legs and a vegetable has no legs at all." (p. 28)
The Giant should of course have referred to our species as human beings. As a noun, the spelling is always being - unless you are talking about vegetables.