It depends. Some changes depend on their characteristics, skinny, fat, etc. We usually add "ito" or "ita" at the end of the name.
Ex:
Pancho = Panchito (Male)
Cristana = Cristianita or Cristy (Female)
Us Mexican's normally use "wey" to friends.
Ex:
Olle! Que ondas wey! = Hey! How's it going man/ girl?
It honestly just all depends our relationship with the person, just like in the English language. If you don't like the person, why give them a nickname? If you love/ like the person, of course we're gonna give them a nickname.
Hope this helps!~
