Just got fired from my job, but within the day I was called by another job for an interview, what do I say?

The experience from my primary job (as well as a personal reference) is why I am getting this call for an interview. I just don't know what to say if they ask about the previous job, which they most definitely will. I figure since my HR wont say much other than my dates working, but do they say anything else, like if i was quit/laidoff/fired or if they ask if they would hire me again. I just want to be real careful on what I say as to not self-incriminate.