Get to know your customer, as in what are his preferences. You need to analyze the customer's body language, personality and his preferences for helping him select the perfume of his choice. If the customer already knows what he's looking for, then it's a quite easy process. However, if the customer is interested in trying something new for a change, then you would require patience to help him go through several samples in order to find the fragrance of his choice.
You cannot help out your customer if you're not familiar with the product range that you possess. One has to be familiar with their products if he's to effectively help the customer in leading to the stuff they're looking for. Customers often don't have a clue about what they want and rely on the salesman to guide them through the process. Therefore it's essential to know that what are you capable of offering to your client.
Help your customer to several samples that would suite his preference in your opinion. Always start with the lower price range, as the customer might fell for something expensive and than leave without buying because he couldn't afford the fragrance of his choice. Sampling is an important phase of the selling process, as you have to guide the customer through a variety of products. If you've figured out his preferences than you can easily help your client decide, as what would suite him best.
Offer your customer a jar of coffee beans to sniff in between smelling fragrances, so that he maybe able to properly distinguish between the variety of fragrances. The strong odor of coffee beans help in cleansing the nasal palate so that the scents don't mix up.
At the end it's your job in assisting the customer in making the final decision. Mostly, customers end up with two or three final choices that they can't choose from, and that's where your expertise come in. Ask your customer a few questions that will help him decide, and then based upon your analysis of his personality recommend him one fragrance, so that he may finally make up his mind.