Just ask enough insightful questions to show that you really really care about:
1. What your going to work on.
2. The quality of your team members.
3. The system they have now and what's planned for the future.
4. How you can make a big impact.<p>All this reflects back on yourself and will get you in 80% of the time. The other 20% requires you to answer puzzles, programming problems etc.<p>I've taken people who can't get to the exact optimized solution I'm looking for but who dint give up easily and whi keep trying till they start to irritate me to no end by nit letting me move onto the next question.