To get my attention, they need to be different. (That's probably obvious.) Not as in look different (though that's okay), and not stand out in a obvious way. I don't like to compete for attention, so if they get many people's attention, they're more likely to lose mine. Talking about dogs or clothes is kinda boring. Talking about sports is quite boring. Asking questions like, "How are you?" or "What's your name?" or "Where do you work?" or "How long have you been here?" also will make you look like a typical, uninteresting person. I want to hear things I haven't heard before. Therefore, I won't provide examples of what to say. Because there's not so much a way to be to get my attention as there is a way to not be.

Another way to get my attention is to seek it in a subtle way. I'm usually willing to provide attention to those who want it, but attention-seeking behavior is generally uninteresting. Questions are a good method: ask me a question and/or suggest I ask you one. But again, it can't be one of the everyday questions I'm already sick of. And specific is always better than general, because vague questions tend to make me confused/uncomfortable, which could make my subconscious associate you with discomfort.

And, of course, if you get yourself associated with something I already find interesting, that gives you bonus points for being able to keep my attention. For example: Be a gamer. Be a multilingual foreigner. Be a cat.