Ask HN: What do you look for when hiring a junior/trainee developer?

I'm looking for my first web developer job and wondering what to expect from the interview. How do you interview junior developers? What do you look for, specifically:

-Do you set programming tests? If so, what kind of tests do you set? -What's the minimum portfolio of work you expect to see? -What kind of questions do you ask? -Do you look for any particular attitude or personality traits?

To clarify, I'm a non-CS graduate looking to get on the first rung of the ladder, so my question relates to introductory jobs with smaller companies rather than top tech firms.