A problem that's often encountered on UX is that often you don't quite know enough about the situation to answer. Or maybe you think you do, you answer, and then the asker notes that your idea is great...but they can't use it because of this major design constraint they didn't mention.
So what makes a good question? What sort of information do you need to make a reasonable answer? Specifically, what is often missing? Things like mockups, what you've tried and what you're trying to do are always relevant. Some other things like audience and specific design constraints may be important. What are the common things you see (or don't see) that keep you from being able to confidently answer a question?
I'm hoping to use the feedback here to make an faq post detailing what information your post should have and when, so we can improve the site for both asker and answerer by making our questions clearer and more answerable.