Be polite. You might run across some people who you just don't think are very nice or would make a very good date. It's important that you not be insulting during speed dating. Remember that speed dating only lasts a short time. Sit through each session and be complimentary toward each potential mate.
Be honest. When someone tells you that you're very attractive or interesting to them but you don't feel the same way, it's important to be honest and not return the compliment. Make sure the person really does know where she stands in your mind. The right way to respond when someone tells you that you're attractive and you don't feel the same way is to respond by saying that the person is very kind to say so but that you really don't think dating her is going to work out.
Let your date know he's a loser if you have to go there. Sometimes during speed dating, the person you're sitting across the table from is far more interested in you than you ever would be in him. It's important that you let him know that he's a loser if he vocalizes his love interest in you more and more loudly throughout your conversation.
Stop the date early if you absolutely have to. If the person becomes incredibly insistent that you're the right one and you don't want to have anything to do with the person, end the date early. While it's polite to wait the entire 6 or 8 minutes, if you absolutely cannot stand it anymore and the person doesn't get the point, stand up and leave the table to go get a drink.