Congrats on your new job! My sister's an excellent salesperson and although I cannot ask her for advice at this moment, I think what she does is she goes up to the people who are looking through a rack and she will say "would you like me to help you find your size?" or "are you looking for a pair of black slacks? I think these over here would look good on you, even better than those, what size do you wear?". She will also comment on their eyes "oh, you have such beautiful blue eyes, this navy top over here will bring them out even more, and it's such a bargain". I know she will look for clothes that compliment the person's appearance, or sometimes look at how they dress and look for a similar outfit, so that she stays within their style of clothing. You wouldn't put someone in conservative clothes in a tiny mini-skirt and halter top no matter how figure-flattering you think it may be.
I know she greets people as they enter because I have watched her do it, and if she gets a "leave me alone" vibe from the customer, she will just hang around their area and pretend to be busy or just stand around and look away, so that they ask HER for help when they need it, instead of going to someone else.
Appearance is very important, believe it or not. She gets a lot of people that comment on how well-dressed she is and they trust her for advice in putting outfits together. Of course, when it comes to selling men's clothes, the men head straight to her and ask her out or ask her if she's a model, so that helps her snag sales.
She also upsells. Say you're buying a white blazer. She will ask about what you plan to put it together with, and offer alternative suggestions ("oh, this blouse would look beautiful with it, don't you agree?") and she will help put the outfit completely. She will walk them over to the shoe department to help select a pair of shoes, and maybe even help them find a necklace or purse as well. The accessories can really make an outfit and she knows that and tries to pass that along to her customers, who tend to be wealthy. She has sold a complete suit, tie, dress shirt, cuff links, and designer shoes to men who were only looking to buy a suit.
Personally, I like a salesperson to help me find my size or help me find something in the same style. For example, if I am looking at a cute Dolman sleeved top but it's a crop top, which means my belly will show, I'd like the salesperson to say "oh, you like Dolmans? Here are some other options in case that one is too revealing for you", instead of having me on a wild goose chase throughout the store. This is even more true if I am with my daughter. I don't want to spend more time than I need to at the store. Unfortunately, no one seems to do that anymore based on my recent experiences at Macy's. I was looking for some white skinny jeans but they only had tiny sizes. The salesperson even pointed out those probably wouldn't fit, but made no effort to find ANOTHER pair of white jeans that might fit. I walked out of the store and decided to buy some jeans on their website instead. I also like getting compliments ("girl, you got some legs! these skinny jeans would showcase them perfectly, and will also show off your waist"). Women are insecure, and just having someone making us feel attractive and helping us look like a million bucks while being friendly and supportive about it can make or break a sale.