I participate on several Stack Exchange sites that have scope that's a little more subjective than the norm. These topics tend to also be more "accessible" to people; you pretty much have to be a programmer to answer questions on Stack Overflow, but anybody who once knew somebody who had a cat might feel qualified to answer questions on Pets. Ditto topics like the workplace, health, writing, parenting, and lots of others -- lots of people have some experience with the topic (or maybe just some speculative theories), but answers work best when they come from a position of relevant expertise. But, to add a wrinkle, sometimes expertise does come from experience; it's just that not all experience leads to expertise.
We would like to raise our overall answer quality, which I think means a combination of attracting more users who can contribute high-quality answers and discouraging the less-informed answers. In this question I want to focus on the latter.
We'd prefer to help the users who are posting the speculative, anecdotal, answers to do better; I'd rather they improve their contributions than go away. People already leave constructive comments and downvote (not enough of the latter, but some) on individual answers; I'm looking for things we can do at a broader level. Ideally I'd like to intercept these answers before they are posted -- that is, find a way to help users think about what's really needed and then do that.
What have other communities done to address this? I know of one Stack Exchange site that has a flowchart for questions, but I haven't seen anything like that for answers. Some sites have rules about citing sources, but that isn't a complete solution -- sometimes an experience-based answer is appropriate. (I imagine that DIY would be very different if that weren't permitted.) What has worked for others?
While this question arises out of Stack Exchange, this isn't a technical question. I'm really looking for a behavioral solution, and there are other communities besides SE that may have addressed this issue.