By example, mostly! I inherited Caro as a part-timer who I turned into assistant manager. She is smart, knowledable, capable and motivated. She does the bulk of the coaching of the other two staff members. She's also excellent at merchandising as well.
So having a strong 2IC is the key for me.
As for friendly staff.....it is part of the Pet Valu Learning System! Truly! Every staff member goes through hours of on-line and book training in customer service and product knowledge. My staff KNOWS that a customer must greeted within 30 seconds of walking in the store. If they seem to know where they are going, we leave them to it for a minute or so. If they seem to look a little lost, my staff is there to direct them immediately.
They all know that engaging the customer in conversation about their pet is the key to upselling and cross-selling. Caro is a master at it. She does it without seeming to be obstrusive, knowing exactly when to walk away.