Face-to-face:
Look at the person and give them a small nod, if they're lucky I might say "Alright.". If I have to introduce myself to a group of people they just get a nod and "Alright.". If they ask me for my name I'll just say it, no need to make a song and dance over people.
Online:
"Hey, I'm *Insert Username for whatever forum I'm on.*."