How can I ask these sort of questions so they are a good fit for Gaming.SE? Do I just say "here's what I want to do, here's what I've done"?
They're about How, and a well written answer will explain Why. They tend to attract long answers, with lots of detail. They're constructive, because you're asking about how to accomplish a task, not simply whether a particular activity is enjoyable.
There's nothing wrong with them, and they are, fundamentally, our bread and butter.
Answers to strategy questions are inherently subjective - "this worked for me" or "this is how I think it can be done". Still, not all subjective questions are automatically frowned upon in this site; you can read more about it in this stack exchange blog post.
In general strategy questions such as "how do I beat this boss" are welcome here. Just ask away, but do try to include details in your question - e.g. what have you tried, what is your specific difficulty, etc.