I have been struggling to find good questions to ask. Fizzbuzz is too easy - and my other questions I try seem to be too hard. So what are your favorite interview questions to ask an average programmer?
Ask how they'd approach the travelling salesman problem.
Given an SQL query, a request, a set of objects and required output, ask them to optimise the whole process from start to finish. The smarter ones will ask about caching, look at optimising the query, look at the way the output is generated etc. The not so good ones will focus on the .NET/PHP/<language>
Hmm.
OK, here's one. Tell them to find out what a Bloom Filter is, and then implement it. Ask what decisions they had to make on the way, and why they made the choices they did.
If you're hiring an average programmer then they need to be able to look up things, understand them, and implement what they've learned. Seeing what they do and how they do it is what's important.