Know the person's name and say it correctly. Privately, ask the person you're introducing to pronounce their name for you. Write the person's name down before the introduction, and give yourself time to repeat it to yourself until you're sure you're saying it right.
Request the class' full attention. Depending on the age and grade level of the group, you might have to wait a bit until they settle down. Ask that all eyes be focused at the front of the room and instruct them to be quiet; you don't want the person being introduced to feel as if she's interrupting, or as if the class is not interested. You also don't want to have to repeat her name several times for the students who aren't listening.
Include details about the person in the introduction. For example, if you're introducing a speaker to your class, you might say, "This is Mr. Robin Wexler. He's the author of "How to get into College with a 2.0 GPA." He's also a professor at the local community college." If you're introducing a new student to the class, you might say "This is Jose. He's transferring from Southeast High. His favorite subject is English Lit, and he played varsity basketball at his old school." Introduce the person in a way that makes your class feel as if they know him.
Make the class introduce themselves. If you're pressed for time, have the class say "Hello," at once, or clap. If you aren't rushing, make the person being introduced feel more comfortable by having the class introduce themselves individually. Have each person stand up and state their name, as well as three interesting facts about themselves. For example, "My name is Sandy. I play in my family's polka band on the weekends. I work at the aquarium after school."