re: Forer Effect - one thing to do is to read all of the personality types, especially before taking the test. I find the these descriptors tend to be a little more specific about traits (especially weaknesses!) and there are many that don't apply to me.

re: self-evaluated multiple-choice - One thing I've done in these sorts of situations is to find concrete situations in which I can say, "when I was in this specific situation that the question was asking about, I did X", which hopefully minimizes the amount of "oh man i want to be an extrovert" sort of answering.

...but yes, agreed, this is really just sort of a goofy little thing, but it's fun and still potentially a bit interesting.