It's a little late for this advice now, but I tell my students to find the students in the class they most trust not to laugh at them...not their friends, and most certainly not their enemies, but the generally good kids, perhaps ones that are somewhat shy themselves, and try to deliver your message to them. Since they are usually scattered about, you maintain some eye contact with the crowd and since these kids aren't likely to make you laugh or torment you, you feel relaxed. After a while you won't NEED to find friendly faces to give a talk, but it never hurts to have them out there!