How should one treat capitalization for titles in the case of replacing proper nouns.
In accordance with the excellent handbook Rules for Writers, Sixth Edition, I always follow the rule as it adheres to family members and high-ranking officials. The text indicates we should capitalize in any instance other than possessive relationships.
I enjoyed my afternoon at the beach with my dad and mom.
We spent the afternoon at the beach, and Dad caught a nice fish in the surf.
Seems simple enough, right? I had an exchange between a father and his son, and that stuff was pretty easy to correct. It gets tricky, though, when we substitute other terms (often nicknames or personal endearments) for proper nouns.
In this case, I opted to leave the terms in the lower case (there was no conclusive discussion of treatment in Rules).
You tried, kid. That's all we could ask.
Thanks for thinking of us, sweetie. That's very kind of you.
An exception would be a nickname that replaces a proper noun through long usage (The Sundance Kid).
It's confusing, to be sure, and one of those nebulous areas of English mechanics that often boils down to house rules. As I read, I pay attention to how publishers deal with these variations, and they certainly lack uniformity.
Just as The New York Times and the Oregonian have their own style sheets, so too do various publishers. It makes it difficult, on occasion, to teach these lessons. That said, the best advice is to adopt a position on the usage and stay consistent.
And I'm one to talk. My novel An Autumn Harvest has been out there in the world for a while (awhile is nonstandard, though not corrected by spell checkers) and I know it needs a brush-up in a few of these areas.