First off, you've probably got some built-up anxiety, you've got even some expectation, maybe even some fear of rejection. So the first thing you do, when you want to attract your crush, is breathe, because you might be tensed up, and you want to approach this guy.
The best way to get his attention is a five-second stare. Just for five seconds, just glance at him to get his attention. Right after that, the best thing to do is just give him a big smile, let him know you're interested, and then maybe even turn away, and then stare at him again.
Guys are a little bit different when it comes to women. We have to make our move toward you. We might actually move around, see where you're at, depending on if it's at a bar or a restaurant. We operate a little bit differently. For women, it's best to keep in one place, get his attention with a stare and a smile. He'll come right toward you.
For men, it is different, because it's more about their actions, what they do. It's not about the stare. Yes, you can have the stare or the smile, but it's more, making your move towards them. Be in their space, definitely helps. And getting eye contact. Eye contact is key when trying to attract your crush.