Should one use an article before a description, as in You should stick to _ rule "think quality". or Look at _ sign "Elderly people"! ? I guess the same rule used as in "Room 4" or "Table 2", i.e. no article used, but who knows... Either way, actually I think this structure sounds a little bit awkward.
There is a place, with a specific rule: You should stick to the rule.
[Did you notice above how I moved from "a rule" there to "the rule"? That's one usage: going from a/an x to the x.]
Therefore, in these sentences: You should stick to _ rule "think quality". or Look at _ sign "Elderly people"!
You should use the: You should stick to the rule "think quality". ///Look at the sign "Elderly people"! ?
1) Rule one: If there is only one of a thing in your limited context: Use the
2) If you move from An Apple to the apple on the table, use the.
Question: "There was an apple around here somewhere. Have you seen it?" Answer: "Yes, I did. I saw the apple. It's on the table over there."
Question: "What do you think of the rule about wearing shoes in the house?" [limited context, only one rule] Answer: "I like it, I like the rule". [or that rule]