The Spanish prefer to do business with those they know and trust. 
It is important that you spend sufficient time letting your business colleagues get to know you.
Once you develop a relationship, it will prevail even if you switch companies, since your Spanish business colleagues' allegiance will be to you rather than the company you represent. 
Face-to-face contact is preferred to written or telephone communication. 
The way you present yourself is of critical importance when dealing with Spaniards.
It is best to display modesty when describing your achievements and accomplishments.
Communication is formal and follows rules of protocol. 
Avoid confrontation if at all possible. Spaniards do not like to publicly admit that they are incorrect. 
Trust and personal relationships are the cornerstone of business. 
Spaniards, like many societies, are concerned that they look good in the eyes of others and try to avoid looking foolish at all times.