As others said- be yourself, be clever and witty, be honest.   I ran one personal add in New York Magazine. I used the headline "A mind is a terrible thing to waste, but so is $20 a line".   I got about 80-100 responses.   Many were very attrctive with high powered carreers.   I went out with about 15 of them.    Most crazy neurotic New Yorkers, but I needed that to get it out of my system.   I met my wife soon after that.   

My favoite personal ad of all time was from the Boston alternative Real paper. It said "I love midnight rides in police cars, Burnt flesh offernings.   Sandwhiches with real sand.....I am looking for a relationship.   No weirdos freaks or phonies please"   I would have loved to see the responses she got.