Right now, Im 17. This happened when I was 15:
I met this girl on the web. She lived in Westchester (I live in NYC). We spoke for a while, exchanged pics, phone numbers, etc etc. One day she was like, I wanna meet you. So we agreed to meet around my house (I didnt tell her it was my house, I just said street address and avenue). In any case, I sat in a Deli across the street, and called one of my friends up (I told him about this) because a. he wanted to hear what she was like and b. I wanted to be able to turn around and have something to do in case I need to bail.
In any case, I was waiting for the 15 year-old beauty to show up and call me. Instead, a 13 year old with a hairy pimply face pops out of a car with her parents and brother inside. She calls me. I just didnt pick it up. Went deeper into the Deli and sat there for about twenty minutes. My friend was laughing his ass off. I was disgusted at the amount of time wasted. After twenty minutes passed, I came close to the exit and looked around. Coast was clear. I went home.
Moral of the story: Always scout it out first. If shes the one telling you to meet her somewhere, have a friend be off to the side. Have it so that if the girl isnt exactly what you were looking for, he'd call you and say its an emergency, explain to her that youre sorry and that you have to run. Storm out, act it out good. Stop talking to her after that. Problem solved.
If theres the chance of Jimmy there showing up, go to a crowded or a somewhat croweded area - you should probably agree to meet in a store or in a mall. Be sure to meet in a place where you can see where the person would come from, and just talk on the phone or something, so that if you get kidnapped you can always call or alert someone or something.
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Go for it, just be ready for every scenario that could happen.