This is a very important challenge for this site, which we've been discussing and attempting to address for a long time, as seen in this very early meta-question on this site's progenitor, mi.yodeya. If you have any suggestions for remedies that we ought to employ that we aren't already, please suggest them.
Unfortunately, the red disclaimer we had at the top of every page, for everyone on mi.yodeya is now relegated to the side, and only for new users (plus the FAQ and the rollover text for halacha on the main site). However, answerers seem to be doing a pretty good job of maintaining the practice of advising people to speak to their own Rabbi for personal advice.
I still stand by what I wrote then, which goes directly to your point about future readers paskening for themselves:
The remaining question is: What if people ignore the warnings and use mi.yodeya information as if it was professional rabbinic advice? I don't have an ironclad answer, but I think that on balance, we're doing OK. People give classes on Jewish law and practice all the time, and there's always the danger that attendees (or archive-listeners) will act on what they hear in the class or in an associated Q&A session without asking their Rabbi first. The danger here is similar and, I think, similarly tolerable, with the advantage that we're explicitly warning against such practice at every turn.
Hopefully, more people will be encouraged to ask their Rabbi questions that otherwise wouldn't have than the other way around, thanks to our questions and answers spreading awareness of the issues and our disclaimers reminding people to go talk to their Rabbi.
Based on Adam's suggestions in the comments on this answer, I've added the following to the FAQ:
Questions that appear to be requests for personal practical advice will be either edited to more general wording or closed.
For more on why it's important to take personal questions of Jewish practice to your Rabbi, see here.
If a question is a blatant request for personal guidance that should be coming from a Rabbi, I will often close it using the "Too Localized" close reason. This is because one of the reasons why it's important to take such questions to your Rabbi is that your particular situation, lifestyle, habits, and communal context can be important factors in determining the correct guidance and actions for you, and that information should not be required to care about or answer a question in this public, permanent forum.