This party sounds different than the parties I talked about. The NYC parties were basically Trans provider Meet and Greets. This sounds like a sex party like the events they have at Rainbow Playground.
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So not to be a dick but.... Yea Duh? Its a sex party, you're looking for someone to casually fuck. Things like personality, wealth and character don't really mean that much. People are going to seek out partners they find sexually attractive. If you are young, in shape and have a big dick more people are going to want to have sex with you. I'm not sure why this is such a controversy when people talk about sex parties. This is how it works in normal situations too. Hot people are in more demand. Sex parties are no different. That being said, I am a fat guy and I have fun at play parties. Here are my hints and tips.
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1) Focus on the things you can control. In the short term this means doing the best with what you got. Work on your clothes and wardrobe. Wearing nice clothes can flatter certain areas of your body while hiding others. Wearing jewelry helps. It might also make sense to get some fetish gear or other sexy outfits (depending on the party). People appreciate it when you put in effort. If you show up to a sex party wearing jeans and a T-shirt, expect the same effort in return. In the long term this means getting your ass in gear. Start going to the gym and working out.  
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2) Be personable. When you are at a play party you still need to talk to people and get to know them before fucking them. Practice being more sociable in normal situations. Strike up conversations with the intent of asking questions and getting to know someone. When you are at a play party, don't just talk to the people you want to fuck. Talk to everyone. Start conversations with people just to talk, not with the goal of fucking in mind. A lot of people don't even fuck at their first play party. They go there to meet people and check out the scene. Of course, if someone doesn't want to fuck you they will blow you off. No big deal, just move on and keep being friendly. Ladies will feel comfortable around you if they see you being kind, confident and friendly to people without the expectation of sex.
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3) Know what you bring to the table. You have to bring something to the table for the other person. In p4p we bring cash to the table. Here we have to bring something different. Some guys bring six pack abs and a huge dick. If you don't have that you need to think about what you do have and display it. Once you know what you offer, your confidence will increase.  
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4) Have realistic expectations. If you're not the hottest guy at the party don't expect the hottest girl at the party to be jumping all over you. P4P can make guys a bit delusional about their own market value. They talk shit about providers who would never even look at them in real life if not for money. Don't harshly judge others. You'll have more fun with realistic standards.