Good questions to ask this person might include where do you see yourself in three/five years time/ten years/thirty years? If they are reasonably serious instructors they will probably be around for three years, although the harsh facts are that most will not be around for ten years, especially if youngish, simply because the pay is shocking at the entry levels. You could also ask them how long have they been flying/instructing for, this would give you an idea of their maturity as a pilot, and you can judge for yourself their maturity as a person.
Sometimes however the instructor/student combination doesn't work, and nobody knows why. I found when I was learning that each instructor (and I had six by my PPL) had their own little hand signals which they expected me to interpret from step one. This obviously couldn't happen, so I got frustrated with each one until I got one for three lessons in a row and she then took me for the rest of my PPL right through to multi-engine instrument rating. So my advice as "sometimes-the-good-one-and-sometimes-the-bad-instructor" of two years going on four years instruction time is stick it out with one instructor for another couple of lessons, and don't be afraid to tell them what you don't like about their instruction! Students keeping quiet on us makes it impossible to function properly because we need feedback to adjust to your needs.
Also, try putting somthing in the Instructors forum, it's getting a bit empty!
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Confident, cocky, lazy, dead.