Well i think the most important is to know the task of the programmer, do you want a web developer? or a desk developer? even a developer to make some bash/scripting in the server? first is so important to know the target and the type of the programmer.
Second is very important to know about the programmer, the motivations, aspirations, what want from working in a company and what are their values.
And i think another important thing to know is the skills they have, is a good programmer? have any good skills in some of the programming?
You have a lot of docummentation in the web about hiring programmer, but i think it's important to know something about programming or have any employee in the company that know about progrraming.