Yes, I remember mine, but it was in another setting.
I was asked to do some magic for kids, well, in the age of 10-12 years. And they knew about it before I came, so, I didn't need to ask anything. They just came running to my table, some very enthusiastic, and some with the setting of "haha, i don't believe in magicians, I'm gonna expose you!". Well, too bad for him, he didn't, and was quiet for the rest of the evening

Anyway, if the guys you are going to magic for, don't know about it, you should find a good reason to approach them. There are couple of ways of course, one could just be to be honest and say, "Wanna see some magic?", but not everyone likes that, but it might work as well. I really don't care anymore. What you could do, is to ask some persons at a table, if they have an item (that you need for a magic trick). Let's say you gonna do a cigarette trick, you just ask for a cigarette.
Finally, introduction MIGHT be important, but it's not a must. The important thing is that your magic is great and maybe fun.
Good luck !