I have trained people quite effectively in three different and very diverse industries. Always the upscale is important. If you are a waitress, give them a reason to order an appetizer, to begin their meal. Tell them that you just saw a pate of ribs come out of the kitchen, and they looked particularly good out of the kitchen tonight. If you don't ask, you don't get. Ask if they would like a side of fresh corn that may not be in the menu, and certainly not featured. The higher the check average, the higher the tip, the more they will enjoy their meal, and the more money the restaurant will make, and more likely you have return customers.
That was only one industry. My career was in the fashion industry, specifically the industry that produces more money then any sector of the retail industry. I would love to take a store manager up to the security room and make her watch the tragic flow through her store. Why do they avoid the cosmetic counter at the front of the store and treat it like poison. I will tell you why now. Every women, and the few men at those counters consider themselves very privileged, and are in no way inviting and applicable. Why do some people flock to other departments, yet do not. Spend time in others? Are they physically blocked off, very poor merchandizing or examine the reason why.
I am an efficiency exert, and can see how things can be much easier, making more money for everyone, and cutting time, work, and costs. Return business means good customer service, as well as access to the things people want most.
Everything falls from the top. If there is shit at the top, then it will all fall down to every level.
In contrast if you have good at the top, I take Apple as an example. Steve Jobs was at the top, and now that he is gone the company continues to provide more invasive, as well as user friendly products. And walk into any Apple Store and you will get the most exceptional service, support, and knowledge that you will ever get in any store, and every employee, just projects enthusiasm. You will always seek to return there.
You want a trainer, they must be sync with what is expected to flow from the top.