How readers approach a poem, or short story, or novel will determine what they find. There is an old saying that everything looks like a nail, if one only has a hammer. If readers engage a work from a vantage point of suspicion that the author is lying to them, perhaps even to himself, they will put the work on trial before engaging in the necessary due diligence.
What does it mean to read charitably?
Charitable reading means taking a poem, story, or novel on its own terms before judging it. The charitable reader sets aside, for a while, the suspicion that the author is lying or mistaken, brings whatever knowledge helps the text be heard, and withholds evaluation until the work has been received as it is.

If they read more charitably, the voice of the text will be more readily discernible. A charitable reading attempts to move the reader, as much as humanly possible, out of the way so the text can be taken on its own terms, and this is the approach I strive to model and teach in my classes at Schole Academy.
It is impossible for readers to remove themselves and their own background, experiences, and knowledge entirely, as if they could become a blank slate. Nor would this necessarily be praiseworthy. For example, a Christian reader — or even a non-Christian reader with some fluency in Christian beliefs and a degree of Scriptural literacy — will be in a better position to hear Paradise Lost as it is. Other times readers may need to intentionally bracket certain feelings, beliefs, or political positions to hear a work which differs in these regards. If someone grew up in the countryside and, for whatever reason, came to despise his or her time there, this recoiling at all things bucolic will need to be set aside to appreciate as much as possible a work of rural literature.
Receiving a book rather than using it
The good reader, according to C.S. Lewis, is one who receives, rather than uses literature. Lewis’s good reader is our charitable reader. “When we ‘receive’ it [a work of art] we exert our senses and imagination and various other powers according to a pattern invented by the artist,” Lewis maintains in An Experiment in Criticism. “When we ‘use’ it we treat it as assistance for our own activities.” For the user, the literary work becomes a means to another end: “as pastime for a dull or torturing hour, as a puzzle, as a help to castle-building, or perhaps as a source for ‘philosophies of life’. The ‘recipient’ wants to rest in it.”

With a charitable reading, we enter into the work before we judge, categorize, or employ it for something else. The work is, and is not for something else. That is, the work has a life of its own, even if it is only actualized in our reading. And it is a charitable reading which provides that actualization.
Charitable reading and the readings of suspicion
Opposed to a charitable reading is one grounded in suspicion. Such critics know the work of literature may be up to no good, even if the authors themselves are oblivious to this. Marxist critics call this false consciousness on the author’s part. The author and the work need not be taken on their own terms. The work itself, in Marxist critic Terry Eagleton’s phrasing, is not even an “expression” of ideology, but rather the “production of ideology.” And the work of literature, this production of ideology, comes from and takes its place in an overarching ideological framework which upholds the ruling class. For such readings of suspicion, the verdict of the jury is in before the case is heard.
A charitable reading hears the case, refusing to bring an agenda to the text, but allowing the text to be what it is. There is no little skill needed in such a reading. Knowledge and experience valuable to hearing the voice of the text must be employed, while at the same time some experiences, or political and philosophical positions, may need to be silenced for a spell so the text can be heard.
Lewis’s language is as apt as it is compelling. We receive the work; we rest in the work; we enter into the work and the spirit of the work to experience it as fully as we can. Once charitable readers have allowed what the literary work is to come to light, they can categorize, evaluate, even perhaps employ the text for other uses, but not until then.
Charitable reading is also the heart of a good Socratic seminar. For more on how that conversation grows from kindergarten to high school, see Socratic Teaching from Kindergarten to High School.