I started on the "till" at a very busy petrol station. Never worked with "the public" before.
Piece of cake.
Rule One. Leave your personal $h!t at home. NEVER bring it to work and inflict it on the customers.
Rule two. Smile, be nice, eye contact.
Rule three. Be Nice, be efficient.
Rule four. Be nice, Talk to the customers, but don't get personal.
Rule five.Be nice, thank them, look over their shoulder to the next customer and smile like they are the 'sun shining out from behind a stormy cloud'. "Hi, how can I help you. ??"
Sounds cheesy ???
Sure, but then I made manager in 12 months from start.
I don't work in retail any more, however I value the lessons I learned.