In Spain, people have a given name or first name (nombre) and two family names or surnames (apellidos), each one of these corresponding to the first surname of each parent.
My full name is, then: Miguel Muñoz Pérez.
My preferred way of signing is 'M. Muñoz Pérez', even if sometimes I may (incorrectly) appear as 'M. M. Pérez' or as 'M. Muñoz-Pérez' in some places. I would cite my own papers by refering to the first surname, i.e. as [MuXX].