I have a very severe stutter. For me its all about practice, man. Practice reading on your own just very very veeery slow, like 3 or 4 times slower than you would normally talk. Doing this you will find you shouldn't stutter what so ever. After that increase your speed while reading on your own, then move onto conversations with a close friend speaking slowly as well. Once you become use to speaking a bit slower in more comfortable situations it should be a lot easier for you in a high stress/unfamiliar situation.