For pre-opening you're not looking to *deliberately* grab her attention. It's more like *accidentally* forcing her to notice you.
There's a few ways it can happen but here's some:
- Eye contact when you're not right near her. If you lock eye contact across the bar for example, she has seem you and noticed you. Fundamentals play a big part... i.e. your eye contact is good and she notices you in a positve way. If you are near her later, she's more open to meeting you as she's already noticed you.
- Another is when you are near her. You don't want to deliberately tap her on the arm or shoulder. But consider you are talking to your buddy near the bar, it's busy-ish. She is standing right to your side. Maybe your arm brushes against hers, it's not a deliberate act like tapping someone's shoulder but your presence is now known to her.
A note on the second one though, you need to make sure its like an accidental thing. I see this being done by guys and girls pretty commonly, actually girls do it quite a lot. They get in your space or brush against you but pretend like they don't even notice you. Guys can be bad at it though, you can see them deliberately easing into a girls sapce, or touching her when it can't really be accidental because they are not in a situation where it could happen.
An example I see is like the one I mentioned above, where 2 guys are chatting, but one is edging backwards away from his buddy while they are talking, there's now a clear space between them like someone could walk through and he's clearly edging back because the girls are directly behind him. This might not come off well unless she already is looking for an excuse to meet you, in which case she might open, but if not, you look kinda weak.
It's a tactic I've seen on toher sites too under different names, usually something like "Forcing IOI's". It's really all about making her "accidentally" on purpose noticing you.