To give yourself a little jump start, you might enjoy seeing the movie He's Just Not That Into You. The main male character owns a bar and watching him will give you a sense of how to talk to bartenders.
In closing, I'd like to give you one more bartender tip. The local bartenders you befriend will know (without asking) how to serve your drinks. If you don't drink alcohol, they'll be happy to make you a non-alcoholic drink, and you can ask for it in any type of glass you wish (my friend used to drink flavored, no bubbles water out of a martini glass). If you do drink alcohol, then to ensure you don't become inebriated (a concern of mine because I'm a light-weight) you can pre-arrange with the bartender to water down your wine with an ice cube or to use less alcohol in your mixed drinks. When you start talking to that man sitting next to you and he offers to buy you a drink, the bartender will already know how to serve you.
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So, give it a try. Visit a few bars. Have conversations with several different bartenders. With each success, your confidence will grow. Before you know it, you'll be taking these skills to other events and you'll find yourself easily chatting with everyone there.