Writing Spanish surnames

by Sharlene
(Highland CA USA)

How do we write Castlian Spanish Surnames in the tradtional manner? If the name is Maria San Miguel Gonzalez do you put "y" or "de" between San Miguel and Gonzales?

We are having a family dispute and it is very important that we use the correct spelling for a special project that we are working on.
Thank you, a quick response will be greatly appreciated.