Best sort of training would be to have experience in a retail environment. Supermarket experience is very desirable. Customer service experience is also very sought after. Also, it is very beneficial that you show you somehow interacted with decision makers and needed to persuade them at one point or another.
Career path leads to Account Management, Merchandising Manager, and could also lead to Brand manager depending on your education and the company. A sales role would also be in the future again depending on the company.
I am a regional merchandising manager and was a retail sales merchandiser.