stuttering and sweating are all good, you'll only do that once and never have to worry about it again... you can even make a joke about it.
running out of things to say, well, that shouldn't be an issue if you've planned a good intro lesson that isn't based around you talking anyway.
here's one I've been churning out for nearly ten years, never fails to get 'em chatting.
1. Teacher Intro
put 5 answers to Qs about you on the board, have the student shout out the questions.
e.g. 27 (How old are you?)
make them progressively more cryptic, I like to end with a woman's name, Wendy, that has them guessing all sorts of relations to me (girlfriend etc etc), but in fact it's the name of a pet turtle that I had in Xi'an in 2005.
Silly, but it breaks the ice.
2. Student Pairwork Intro
Ss do the same thing. First they have 5 mins to write 5 answers to Qs about themsleves, secretly, on a piece of paper, then they swap answers with a partner and try to guess each others questions.
Tell them in advance to make them a little tricky if possible, and to make note of their partners Q+A, because in the end they will have to introduce their partner to the class.
Depending on the size of your group, that is a nice 50 minute class period, with techer-performing time cut down to introductions and explanations.
ONce you get this first class out of the way you will have an idea of their level, and you won't be nearly as nervous standing up in front of them again.