back off, little man!

I just had a first. I got asked out on a date on myspace. Ick. That's worse than the aroma coming from the litter box right now.
I'm not good at telling people "Hell no, I won't go to lunch with you, you strange little man." Especially when it's not face to face. It's much less abrasive, I think, when I let my body language give the F. off vibe. Don't you agree? Oy ve.
To anybody that reads this, I need advice on how to tactfully turn people away. And telling people I'm in a relationship doesn't do the trick because no one in this awful town respects long distance relationships. Help.