I am in the same boat as you. Working part time in a beauty boutique, as well as being a demo rep.
From my experience, every client in your seat or person who walks up to you is a sale. It's all about knowing your product and engaging the client.
Compliment them and start a conversation. Always have a smile and be welcoming. Even if they don't buy that day, educate them, write down the product, let them know who the counter manager is. This way they feel comfortable to come back. Always let them leave with a positive experience.
I always give mini eye massages to each person who walks by, and 75% of the time, I sell one thing or another.
Hope this helps
It's all about confidence, knowledge and smiling
The more product knowledge you know, the more likely you are to sell. That goes for working in the boutique as well.