Comment vous appelez-vous? Comment t'appelles?
The first one is in formal contexts, viz. you are meeting the person for the first time, the person to whom you are speaking is a hierarchical superior (whether in a work or a family or other social context).
A bit more detail :-
Business contexts : you would almost certainly use "vous" forms when addressing your boss. In trendy contexts, this would either not happen at the outset, or he/she would very soon suggest that the "tu" form be used. Outside business contacts would expect this form to be used.
Social contexts : friends, colleagues (on the same rung of the work ladder), students, sportsmen and women all use "tu" forms from the word go, or almost immediately. Adults addressing children (known or unknown) do too. Children take some time (nowadays) to use the "vous" form with adults, although they ought really to use it. (My husband "vous-ed" his parents, unusual now!) When I worked in sailloft here for a while, it was "tu" in both directions from the boss, which seemed odd in fact. Otherwise, when teaching in a college, I used "tu" to pupils, which was the school's policy. They "vous-ed" me. When lecturing at university level later, "vous" was used all round.
These are not rules, guidelines really. As a general rules, start with "vous" and when the French native is ready, "tu" will be suggested when appropriate.
Visiting France since 1977, lived here in 1981-82 and since 1991...