2. So she can manipulate patrons like pawns
Which could mean, say, asking a group of girls to slide down a stool closer to you to make room for another party, even if there is no other party.
3. She can tell you what someone's drinking
If you want to buy a woman a drink, you should buy her something she'll like (so, probably not a Bear Fight). Asking your bartender what the lady you’re after is drinking is a simple way to demonstrate, to both the bartender and said lady, that you’re both considerate and interested.
4. She can assess potential, and keep you from going down a dark path
According to Nora & Phoebe, this could mean telling you "No, that girl is not into you. I just heard her talking about her boyfriend," or "No you shouldn't be into that girl. I just heard her tell her friend that she faked a pregnancy to get back at her ex-boyfriend." Your bartender also has the scoop on all the regulars, which is nice.