Be open and upfront about your stutter. Mine can get pretty bad too, some days are just worse than others. I interviewed for a few jobs out of college a little over a year ago and I always felt much better opening with the fact that I have a moderate to severe speech impediment. I found it put all parties at ease. I'd start off by saying "Before we start, I'd like to let you know that I do have a speech impediment that can interfere with or sometimes completely block my speech; I hope that's okay." They always seem to understand and are pretty supportive.