Selling wine from a retail shop takes a person who is knowledgeable, fair and honest. Over the past 40 years I have worked at three wine retail shops. My primary job was to educate customers about wines and help them select the wine for them.
Knowledgeable This is a key ingredient for any salesman. To properly sell any product you have to know and understand that product. 
Many times a customer would select a bottle of wine and ask me how it is. If I have never had that wine, my answer would be. I have never tasted that wine, but the vineyard has a good reputation, the grape from that region is known for its light and fruity appeal. So, I am going to assume, its going to be something like that. If you would like, I could show you something that I have personally tasted and is in the same grape and price point. The worse thing any salesman can do is try to make up a story, lie to the customer about the product. Its much better to just say, I dont really know, but I will find out
Fair When a customer comes in looking for a bottle of wine to serve with dinner, I would generally ask three questions
1. What are you having for dinner?
2. Are you an avid wine drinker or just starting out?
3. What is your price point?
This sets the stage so that I can start narrowing down the type of wine that I believe would best suite the customer. Play fair. Keeping in mind the answer to those three questions, should allow you to select a number of different wines. Once I do get it down to a few, then I ask more questions about their likes and dislikes about wine. I also tell them to throw away the notion that you have to have White wine with Fish and Red wine with Meat. Whats more important is what you like. If you dont like dry wines, but prefer sweet, then I will find a nice sweet wine for you.
Honest This is so much easier for a wine salesman than the owner of the store. The owner needs to make sure the store is profitable, so they purchase wines that will give them the largest return of profit. Sometimes those wines are good, but at times they are just borderline. 
So, when the owner works with customers, more than likely they are going to direct the customer to those wines. Its all about the money to them and it is their business. Now on the other hand, since, I had no direct ties to profit, I do not have to worry about the profit margins (but still as an employee, I do have to keep that in mind) I could find wines that would be best for the customer, not what is just best for the store. It could be one of those sale wines, but the key here would be to find the right wine for the person. My biggest thrill is when a customer comes back and tells me how much they liked the wine I selected for them. At that point, I’ve established trust and confidence with the customer and they will generally allow me to select their wines for them in the future.
ONE MAJOR TIP FOR WINE SALESMAN
Never talk big wine snobbery words to a customer. You do not need to use a lot of fancy wine jargon or terms that may go right over the head of a new customer. Try to identify their level of wine experience and work with that. Make the customer feel comfortable with you. That will go a long way.