There are many styles of puzzles, but my favorite may be the keyword. The downside is you can't get the coordinates unless the 2nd party checker is available and working. You are also required to give a specific answer that is spelled correctly. Yikes. In this case use the certitude to ensure you have the correct keyword, link is below and it will give you the coordinates.
So how do you get the keyword? Is it a question, a fill in the blank, white text on the cache page, a riddle, hidden in the source code, on a nearby benchmark, or is it hidden in the text somewhere?
This one is a question.
What would a birch say is his family name?
"Betula"
You can validate your puzzle solution with certitude.