sheikha, it all depends on what nationality, and on what type of visa you are travelling. The embassy asks lots of questions, i think, depending on the nationality.In our Office, we both applied for German visa on the same date. I got it on the 3rd day, my colleague got on 16th day !!
Better you arrange an invitatin letter from any company in Spain inviting you "to deliver a speech / consultancy" etc. You need to show , sometime , a hotel resrvation etc etc..
Just check with the Embassy. I think Shengen states all have the same rules, right ?