Here are two key questions to ask a programmer for how they approach programming both in and out of the financial sector:
1) Are you familiar with object-oriented programming, and do you use it frequently?
2) What error testing methodologies do you use?
These are very basic questions, but it filters out a lot of people. For question 1, the person should answer yes. If they say no, it should be for performance reasons, or because the scope of the project does not require it. For question 2, you want a person to definitely mention unit testing and debugging the software through trial and error. Once again, these are basic things for a good programmer. If you want, contact me regarding any programmers you are considering, and I'll give you a hand evaluating them as time permits. I have a programming background myself, and I interview and hire other programmers fairly often for work, so this is something I am familiar with.