How can I get the attention of someone I've never met?

Do it the old fashioned way. Go there, despite saying that you can’t get there. Pop in and chat. She will never know if she likes you if she hasn’t even heard you talk. (Unless she is bonkers).

After a few chats, or even after one chat if you feel it is going well, offer to take her to dinner or lunch. It is that simple.

Either do what LornaLove says or write her a note telling her you would like to get know her and giving her your phone number. Leave it for her at the bar.

Please be very careful about how you approach such a person. A server in a bar will often make eye contact with customers to see if they need anything. The chances are excellent that she gets hit on quite often. If you are really interested, put your name and # on a piece of paper, then during a quieter time (for her) approach her, introduce yourself, say that she looks interesting (or something equally non-threatening) try a statement like “I’d love to meet for coffee sometime, here’s my # ” hand her the paper, then LEAVE. If she never calls, respect that.
I spent a lot of years serving booze and bartending, and was very rarely interested in someone who approached me at work.
Good luck.

1) this bar is not really close by so I can’t just drop in that often

You really only need to “drop in” once. Go back on the same night of the week as the first time, and then do what @canidmajor says.

And the distance acts in your favor because it will deter you from hanging out there which would be creepy.

@canidmajor I was sitting at the bar, so the bartender was serving me – she was waiting on a couple tables so she had no reason to ever see how I was doing. PLUS I was actually dd that night so I only had water :P

It sounds like just going back again is probably my best option, thanks everyone.

Have you tried to introduce yourself, that should work

@bb9335 : Maybe she is indeed into you, maybe she saw you looking at her a lot and was keeping an eye on you in case she had to take evasive measures. I still recommend my approach if you want to be non-creepy. Assumptions made about someone from some eye-contact at their place of business, where they are required to behave a certain way around the customers, can be way off base, which is why I suggest you make a quiet introduction then leave everything else up to her.
Anything more aggressive could, not unreasonably, be construed as threatening.