Usted or Tu with customers in retail setting

Question

Que OndaThis is one of the nuances of usted that I still haven't quite figured out. At my retail job, I often assist Spanish-speaking customers. However, I am not sure if these situations warrant using more formal language. In English, I address my customers politely with "Sir" or "Ma'am" but the language I use otherwise as I'm assisting them is more informal. I want to maintain the same tone of politeness yet casualness in Spanish as English but I don't know if it comes across as too formal. For context, I am in my early twenties and the customers I've spoken to are almost always older than me ranging from their thirties to more elderly people. Obviously, for my older customers, I would use usted but would it be necessary to use usted for people who are not that much older than me? I don't know if there is anybody here who can shed some light on this topic. In Spanish-speaking countries do retail employees typically address their customers with more formal, usted language?Thank YouNathan

Accepted Answer

Hola Nathan
Good question but a tricky one as there is no perfect answer for this.
If you are in retail assisting customers the "general" rule would be to address the customer formally, e.g. ¿Le puedo ayudar? ¿Desea usted algo más? Firme usted aquí, por favor, etc. This normally happens with both young and elderly people.
However, this "general" rule relaxes depending on the type of establishment. For example, if you are serving in a bar and you have customers who are young, you can address them as "tú" and this won't be shocking at all. It sounds more natural to do this with young people, actually. It will also depend of course on the specific policy of the establishment; your boss might like a general formal approach to all customers, so you need to be more formal in general in this case.
This is what happens in Spain and I am pretty sure this is what applies in Latin America too, although maybe slightly more formal there, I believe. 
Very often you start treating customers calling them "usted" and as the conversation flows, you may ask your customer "¿le puedo tutear? meaning "Do you mind if I use "tú" with you?" - the customer generally say "claro" (of course), and then you drop the formality all together. 
"Tutear" is an interesting verb in Spanish. 
I hope this clarified it.
Saludos
Inma