In today's more relaxed business environment it is not uncommon to refer to people by their first names, even when you have never met in person. In Mexico, the business environment tends to be much more formal (in general, but it also depends on your industry). Titles are very important, so when you are addressing someone in an e-mail or in person be sure to refer to them by their title and their last name until they tell you otherwise.
Some popular titles in Mexico:
Lic. (pronounced as "lick" in English) - this is short for Licenciado or Licenciada and it refers to someone who has an undergraduate degree, or licenciatura. Basically a way to show you made it through college. A Licenciado can hold any number of degrees from business administration to law.
Ing. - this is short for Ingeniero or Ingeniera, someone who has a degree in Engineering.
Arq. - short for Arquitecto or Arquitecta, which means Architect. It may seem strange to say "Arquitect Rodriguez", but it is a formality that is very much appreciated.
Sr. - short for Señor.
Sra. - short for Señora, this is the equivalent of Mrs. in English.
Srta. - short for Señorita, refers to an unmarried or young woman. When all else fails, use Senorita instead of Sra. You will never offend someone for making them feel younger!
Names in Mexico
Many foreigners are confused by what seems to be a lot of names in Mexico. I'm going to show you how the naming sequence works.
Let's take Arq. Rodriguez as an example.
His full name: Luis Fernando Rodriguez Villanueva
First name: Luis
Middle name: Fernando
Paternal last name: Rodriguez* (this is the name you will refer to him by)
Maternal last name: Villanueva
Let's say Luis Fernando is married to Gabriela Fernandez Coto. Her name becomes Gabriela Fernandez de Rodriguez. Let's say they have a son named Jaime. Jaime's full name would be Jaime Rodriguez Fernandez. The first last name is always the paternal last name and the second is always the maternal.