1. Do not interrupt her when she is talking to someone else

It is a very wrong move to interrupt someone who is talking just have yourself into the conversation.

If she is alone... 

Politely ask her why she is alone because psychologically when you ask or remind a woman at the bar that is all alone and/or has no one else to talk to, she will feel the need to talk to someone; that is you!

Allow the conversation to come in naturally. You can say something about a joke you once heard or talk about the bar or even make a comment on whatever game played on the TV. 

2. Ask her what she is drinking

Here is the thing...

There is nothing as attractive to a woman at the bar as a man who knows a lot about his drinks and can also prove it. If you fall into this category of knowing your drinks/alcohol and can also prove it, you have to yourself a bonus step of starting a conversation with a woman. 

Open up a conversation by asking what she is drinking, then inform her about what she should drink; remember, ensure she is super aware that you know more than she does about drinks. 

3. Never start with anything that has to do with politics or the government

You must have heard this before, but if you haven’t, it is worth repeating - never start a conversation with a woman at a bar with politics. Even if you are only interested in a light chat, do not bring up politics.