If you really want to find out what your date is really like, ask her a question that puts her on the spot. In other words, ask a somewhat outrageous but straight forward question where her sub-conscious would yield an initial “Who does he think he is?” response.
Now her response doesn’t really matter here because you’re actually more interested in how she reacts. I love a woman who knows how to handle herself under pressure (who doesn’t!) so questions like “Are you a good kisser?” or “What can you bring to the table if you and I were to get married?” would really get her thinking and hence, put her on the spot.
The trick to making her think you’re “serious” here is to make sure that you keep a straight face at all times. You need to make it clear to her you are merely joking after she gives you her response or else she’ll think that you’re just plain weird!