The first message is the hardest part of the whole process, and it's the part almost everyone gets wrong. You found a listing you like, you're ready to reach out, and then you stare at the screen trying to figure out what to say. Most people default to 'Hey' or 'How's your night?' and then wonder why they never hear back. The first message doesn't need to be brilliant, but it does need to be better than that.
Show you read the listing. This is the single most important thing. Reference something specific from their post, something that shows you didn't just look at the photos and fire off a message. If they mentioned they like a certain neighborhood, a certain kind of bar, a certain kind of music, bring it up. 'I saw you're usually around Midtown on weekends, I know a great spot on Peachtree if you're ever looking for a change' is a hundred times better than 'Hey what's up.'
Keep it short. Two or three sentences. Enough to show you're real, you read the listing, and you have something to say. Not so much that it feels like work to read and respond to. The goal of the first message is to start a conversation, not to deliver a monologue. If you write a paragraph, you're asking them to write a paragraph back, and most people won't.
Ask a question. End with something easy to answer. Not 'What are you looking for?' which is too heavy for a first message. Something light, specific, and easy to respond to. 'Are you more of a dive bar or cocktail lounge person?' gives them something to work with. It shows you're thinking about actually meeting, and it gives the conversation a natural next step.
Don't be sexual in the first message. This should be obvious, and it's the reason a lot of messages get ignored. The listing is on a site that's clearly about adult connections, and everyone involved knows what the endgame might be. You don't need to bring it up in the first message, and doing so signals that you're more interested in the transaction than the person. Let the conversation get there naturally. If the listing was clear about what they're looking for, you already know the direction.
Don't double message. You sent a good first message. Now wait. If they respond, great. If they don't, move on. Sending a follow-up two hours later asking 'Did you get my message?' is the fastest way to go from 'interesting' to 'problem.' People have lives. They check messages when they check them. If you're the kind of person who needs constant reassurance, that's something to work on, not something to project onto a stranger.
The best first message is one that sounds like you. Not a template, not a line, not something you found online. A few sentences in your own voice, referencing something real from their listing, ending with an easy question. That's it. It's not complicated, but it takes more thought than most people put in, which is exactly why it works.