Oh there are ways to do it, of course, but short of making it another full-fledged player in the story, it is rather hard to do.
Sure, if you choose to make one of your lead characters a priest/former-priest/priest-wanna-be then his struggle with his religious vows is key in the plotline. No problem there. Just tell the story and the readers will get it.
Or if you are writing in a series particularly targeted to a Christian crowd, per se, then the limitations and extremes are fairly well-defined for you. More than likely you will not turn off a reader by leaning hard on the aspects of the character’s beliefs.
But, if the chosen faiths of the cast are important to the characterization of each person but not necessarily to the whole Romance (Big “R” #1) of the tale, a quandary is often had as to how much religion to include?
An up-and-coming author can rarely afford to alienate a large chunk of their audience. And that is a risk when you linger a little too long or a little too heavily on the whole Religion (Big “R” #2) of the thing.
Writing a novel set in the late Colonial era, a time in which religion was a driving factor in most everybody’s life in some manner or another, I’m finding myself a little unsure about how to address these issues of faith. How much do I include? How much do I turn a blind eye to?
I have no answers here.
Bummer, I know.
But sometimes just asking the question, admitting there is an issue to be discussed is a start, right?
After all, (to circle cleverly back around to the opening analogy), you must admit there is a fish before you can net it.