I have a low to moderate stutter.In such occasions what I usually do is write down what I want in a piece of paper and recite from that paper.My speech now has drastically improved but when I was younger and had to ask for directions,order food ask any questions to teachers etc I used to jot down the important points in a small paper and show it to them or recite from that paper pretending as if I was unsure of what I wanted.I wouldn't say it is a permanent or perfect solution but that is what helped me then.I sometimes use this tactic in high stress situations like interviews and ask them for a sheet of paper so that I can explain my answers further, diagrammatically.