Terry Gillen, a trainer and consultant, ran this interactive workshop about job interviews.
First impressions are important, he said, and you can relax because much of your first impression is visual: e.g. making eye contact, smiling, having open body language, looking pleased to be there. You can practice with the receptionst and person taking you up to interview room. If the interviewers are comfortable as you walk thourgh the door, they will make favourable impressions afterwards.
He suggested mentioning at the interview that you stammer. You could say that you 'sometimes' stammer. If you like you can raise the issue of diversity; he said this is company policy in many organisations these days, not just to avoid discrimination but to ensure fresh thinking, creativity and 'richness' of different people and their views.
There is much more in his workshop handout notes (pdf).
From the Winter 2009 edition of Speaking Out, page 8.